Problems with Ctrl-z (undo)

[SegundoBob]

For the last few weeks at least, I've had trouble with Ctrl-z undoing way too much.  I have not filed a bug because I have no idea how to reproduce it and I haven't been able to figure out what it does when it misbehaves.  The most bizarre misbehavior I've seen seemed to undo changes that I had previously saved to disk.  This seems very unlikely, but after I did only one ctrl-z, my outline file was not marked "dirty" and a search on a string I had added to three or four nodes could not find the string at all.  Exiting without saving and re-opening my outline seemed to recover the changes I had saved prior to the glitch.

Has anyone else had similar problems recently?