Steps to reproduce:
I have a scheduled SX setup to automatically add a fixed amount of interest 
to a savings accounts at the end of a month.
1. Open the Scheduled Transaction Editor
2. Select a scheduled transaction to edit it.
   The transaction I tried is created automatically once a month. 
3. I changed this SX so that the amount is a variable from this point forward.
4. I removed the check box for 'Create automatically' since SXs with variables
   can not get created automatically.
5. I click 'OK' to save the changes.
6. Now, when I'm trying to close the tab of the "Scheduled Transaction Editor"
   (I have the "Close Button" on each tab) GnuCash hangs and I have to kill 
   the application.

The only message on the command line is this:
  *** glibc detected *** gnucash: corrupted double-linked list: 0x43405158 ***

I have tried to change this SX several times on two different systems (one 
running FC5 - svn r16583 on 2007-11-14 and one running FC6 - svn r16372 
2007-07-29) with the same result except that the error message is not 
displayed on the FC6 system.
Both systems are pretty much standard Fedora systems, FC5 running as a workstation, FC6 running as a server.

Choosing a different SX to modify in the same way results in the same problem.

Stack trace:
The only message on the console is:
  *** glibc detected *** gnucash: corrupted double-linked list: 0x43405158 ***

Please let me know if I need to provide a stack trace.

Other information:
Please let me know if I you need additional information/data/etc.