I am having similar problems with tool palettes now. I cannot add anything to any new palettes that I create.
I have created about 20 palettes previously with no problems, but now after I create the new palette i have tried to drag and drop lines and blocks from the current drawing and also drag and drop blocks from design center, but they are not added to the palette (I even see the little rectangle and plus sign symbol). If I drag and drop these same items onto and existing palette it works as expected.
It's almost as if the palette isn't really being created. I see it when AutoCAD is open, but if I look in the palettes folder it is not there and if I close and reopen the program it is gone.
The palette files are located on a network folder and I am one of the few people that has write permission to his folder and I don't have the lock icon on any of the palettes (new or existing).
I am stumped.
Anybody have any ideas?