Installed SP3 for FP1 today and the problem was still there. I re-read your last post and check the customizations. There were none for this screen. I tried running it in Standard Mode (which I thought I had already tried) and it worked. I changed to All Users and it still worked. I changed back to Self and it still worked. Logged out and back in and it still works as Self.
After I installed SP3 for FP1 the symptom had changed slightly. After hitting save the screen froze (before it was giving the error). When I told Windows to try to "Recover" from the program failure it popped up an error that said "unique index named gltran0 has not been found for table gltran". I used the script in \DB\Scripts to just rebuild the GLTRAN indexes. The rebuild completed fine. After that I tried it again and this time the Message 156 error popped up like it did originally.
So at this point it seems to be working but I have idea why. Thank you for your help. I'll let you know if it shows up again.