From redhat bugzilla at:
https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=205643

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Today I found I was unable to burn some ISOs on CD-RW discs which were not
empty.  The volume name of the CDs had spaces in it, with the result that
unmounting the volume failed.

Version-Release number of selected component (if applicable):
2.14.3-1.fc5

How reproducible:
Every time

Steps to Reproduce:
1. Insert non-empty CD-RW with volume name containing a space
2. Invoke nautilus-cd-burner to burn a new ISO onto the disc
3. 
  
Actual results:
Nautilus-cd-burner fails with a non-specific error message

Expected results:
Nautilus-cd-burner unmounts the disc, erases it and burns the new image

Additional info:

Session error messages:

(nautilus-cd-burner:12478): GLib-CRITICAL **: g_error_free: assertion `error !=
NULL' failed
umount: /media/RHEL_4-U4\040x86_64: not found
eject: unmount of `/media/RHEL_4-U4\040x86_64' failed

** (nautilus-cd-burner:12478): WARNING **: Couldn't unmount volume in drive:
/dev/hdc

(nautilus-cd-burner:12478): GLib-CRITICAL **: g_error_free: assertion `error !=
NULL' failed
closing