Thanks for reporting this bug.

This also occurs on Linux FC14.
In General Ledger do Reports->Account Report.
I get the following output when started from the command line with --logto stdout

 558: 26  (let* (# # # # ...) (if multi-rows? #) (if multi-rows? # #) ...)
 579: 27* (if multi-rows? (for-each (lambda # #) (xaccTransGetSplitList #)) ...)
 580: 28  [for-each #<procedure #f (split)> (#<swig-pointer Split * a40bba0>)]
In unknown file:
   ?: 29* [#<procedure #f (split)> #<swig-pointer Split * a40bba0>]
In /home/mikee/progs/share/gnucash/guile-modules/gnucash/report/standard-reports/register.scm:
 581: 30* (if (string=? # #) (accumulate-totals split total-collector ...))
 581: 31* [string=? #f #f]
/.../share/gnucash/guile-modules/gnucash/report/standard-reports/register.scm:581:31: In procedure string= in expression (string=? (gncAccountGetGUID #) (gncAccountGetGUID #)):
/.../share/gnucash/guile-modules/gnucash/report/standard-reports/register.scm:581:31: Wrong type argument in position 1 (expecting string): #f

Tony: Just to check it's the same on a MAC, can you run GnuCash from the command line and post the last couple of lines of output?

@Tony: In other words, can you please look up the trace file content http://wiki.gnucash.org/wiki/Tracefile after that error and include it here in the bugreport. Thanks!

Here are all the lines from my gnucash.trace file concerning the report; the last line does match:

* 09:58:58  WARN <gnc.scm> In /Applications/Gnucash.app/Contents/Resources/share/gnucash/scm/report.scm:
 638: 15  (if (and (not #) (gnc:report-ctext report)) (gnc:report-ctext report) ...)
 646: 16  (let ((template #) (doc #f)) (set! doc (if template # #f)) doc)
 649: 17* (set! doc (if template (let* (# # # ...) (if # # ...) ...) ...))
 649: 18* (if template (let* (# # # ...) (if # # ...) ...) ...)
 650: 19  (let* (# # # #) (if # # #) (gnc:report-set-ctext! report html) ...)
 652: 20* [general-journal-renderer #]
In /Applications/Gnucash.app/Contents/Resources/share/gnucash/guile-modules/gnucash/report/standard-reports/general-journal.scm:
 126: 21  [reg-renderer #]
In /Applications/Gnucash.app/Contents/Resources/share/gnucash/guile-modules/gnucash/report/standard-reports/register.scm:
    ...
 707: 22  (let (# # # # ...) (if invoice? #) (set! query #) ...)
 729: 23* (set! table (make-split-table splits (gnc:report-options report-obj) ...))
 729: 24* [make-split-table (# # # # ...) #<procedure dispatch (key)> "Debit" ...]
In unknown file:
   ?: 25  (letrec (# # # # ...) (let* # # # ...))
In /Applications/Gnucash.app/Contents/Resources/share/gnucash/guile-modules/gnucash/report/standard-reports/register.scm:
 619: 26  (let* (# # # ...) (gnc:html-table-set-col-headers! table #) ...)
 631: 27* [do-rows-with-subtotals () (# # # ...) ...]
 540: 28  (if (null? splits) (begin # # #) (let* # # # ...))
    ...
 558: 29  (let* (# # # # ...) (if multi-rows? #) (if multi-rows? # #) ...)
 579: 30* (if multi-rows? (for-each (lambda # #) (xaccTransGetSplitList #)) ...)
 580: 31  [for-each #<procedure #f (split)> (#<swig-pointer Split * 1e7e4398>)]
In unknown file:
   ?: 32* [#<procedure #f (split)> #<swig-pointer Split * 1e7e4398>]
In /Applications/Gnucash.app/Contents/Resources/share/gnucash/guile-modules/gnucash/report/standard-reports/register.scm:
 581: 33* (if (string=? # #) (accumulate-totals split total-collector ...))
 581: 34* [string=? #f #f]
/Applications/Gnucash.app/Contents/Resources/share/gnucash/guile-modules/gnucash/report/standard-reports/register.scm:581:31: In procedure string= in expression (string=? (gncAccountGetGUID #) (gncAccountGetGUID #)):
/Applications/Gnucash.app/Contents/Resources/share/gnucash/guile-modules/gnucash/report/standard-reports/register.scm:581:31: Wrong type argument in position 1 (expecting string): #f

*** Bug 639265 has been marked as a duplicate of this bug. ***

Same problem in Windows XP: here's the trace:  * 05:41:34  WARN <qof.engine> [guid_init()] only got 1624 bytes.
The identifiers might not be very random.
* 05:42:09  WARN <gnc.app-utils> Could not spawn perl: Failed to execute child process (No such file or directory)
* 05:42:13  WARN <Gtk> Could not find the icon 'gtk-fullscreen'. The 'hicolor' theme
was not found either, perhaps you need to install it.
You can get a copy from:
	http://icon-theme.freedesktop.org/releases
* 05:42:15  WARN <gnc.engine> Got a NULL guid_list but the QofGuidMatch is not MATCH_NULL (but instead 1). In other words, the list of GUID matches is empty but it must contain something non-empty.
* 06:47:41  WARN <gnc.engine> Got a NULL guid_list but the QofGuidMatch is not MATCH_NULL (but instead 2). In other words, the list of GUID matches is empty but it must contain something non-empty.
* 06:47:41  CRIT <gnc.engine> xaccAccountGetColor: assertion `GNC_IS_ACCOUNT(acc)' failed
* 07:05:31  CRIT <gnc.app-utils> gnc_option_set_selectable: assertion `option->odb->set_selectable != NULL' failed
* 07:05:31  CRIT <gnc.app-utils> gnc_option_set_selectable: assertion `option->odb->set_selectable != NULL' failed
* 07:05:31  CRIT <gnc.app-utils> gnc_option_set_selectable: assertion `option->odb->set_selectable != NULL' failed
* 07:05:31  CRIT <gnc.app-utils> gnc_option_set_selectable: assertion `option->odb->set_selectable != NULL' failed
* 07:05:31  CRIT <gnc.app-utils> gnc_option_set_selectable: assertion `option->odb->set_selectable != NULL' failed
* 07:05:31  CRIT <gnc.app-utils> gnc_option_set_selectable: assertion `option->odb->set_selectable != NULL' failed
* 07:07:22  WARN <gnc.engine> Got a NULL guid_list but the QofGuidMatch is not MATCH_NULL (but instead 2). In other words, the list of GUID matches is empty but it must contain something non-empty.
* 07:07:24  WARN <gnc.scm> In C:\Program Files\gnucash\share\gnucash/scm/report.scm:
 646: 16  (let ((template #) (doc #f)) (set! doc (if template # #f)) doc)
 649: 17* (set! doc (if template (let* (# # # ...) (if # # ...) ...) ...))
 649: 18* (if template (let* (# # # ...) (if # # ...) ...) ...)
 650: 19  (let* (# # # #) (if # # #) (gnc:report-set-ctext! report html) ...)
 652: 20* [general-journal-renderer #]
In C:\Program Files\gnucash\share\gnucash/guile-modules/gnucash/report/standard-reports/general-journal.scm:
 126: 21  [reg-renderer #]
In C:\Program Files\gnucash\share\gnucash/guile-modules/gnucash/report/standard-reports/register.scm:
    ...
 707: 22  (let (# # # # ...) (if invoice? #) (set! query #) ...)
 729: 23* (set! table (make-split-table splits (gnc:report-options report-obj) ...))
 729: 24* [make-split-table (# # # # ...) #<procedure dispatch (key)> "Debit" ...]
In unknown file:
   ?: 25  (letrec (# # # # ...) (let* # # # ...))
In C:\Program Files\gnucash\share\gnucash/guile-modules/gnucash/report/standard-reports/register.scm:
 619: 26  (let* (# # # ...) (gnc:html-table-set-col-headers! table #) ...)
 631: 27* [do-rows-with-subtotals () (# # # ...) ...]
 540: 28  (if (null? splits) (begin # # #) (let* # # # ...))
    ...
 558: 29  (let* (# # # # ...) (if multi-rows? #) (if multi-rows? # #) ...)
 579: 30* (if multi-rows? (for-each (lambda # #) (xaccTransGetSplitList #)) ...)
 580: 31  [for-each #<procedure #f (split)> (#<swig-pointer Split * 7f873a0>)]
In unknown file:
    ...
   ?: 32  (begin (f (car l)) (lp (cdr l)))
   ?: 33* [#<procedure #f (split)> #<swig-pointer Split * 7f873a0>]
In C:\Program Files\gnucash\share\gnucash/guile-modules/gnucash/report/standard-reports/register.scm:
 581: 34  (if (string=? # #) (accumulate-totals split total-collector ...))
 581: 35* [string=? #f #f]
C:\Program Files\gnucash\share\gnucash/guile-modules/gnucash/report/standard-reports/register.scm:581:31: In procedure string=? in expression (string=? (gncAccountGetGUID #) (gncAccountGetGUID #)):
C:\Program Files\gnucash\share\gnucash/guile-modules/gnucash/report/standard-reports/register.scm:581:31: Wrong type argument in position 1 (expecting STRINGP): #f

Thank you for your report. I have manage to trace this problem back and committed a fix in r21518 (trunk) and r21519 (2.4 series). The fix will appear in the next maintenance release of the 2.4 series.

*** Bug 659533 has been marked as a duplicate of this bug. ***

GnuCash bug tracking has moved to a new Bugzilla host. This bug has been copied to https://bugs.gnucash.org/show_bug.cgi?id=639082. Please update any external references or bookmarks.