Dryopithecus for posting this. There seems to be more than one issue involved here. PB has two separate Undo/Redo functions for Notes, one in the main Edit (ME) menu (no mnemonics), and one in the Notes Edit (NE) menu ( Ctrl+Z/Ctrl+Y). If you commence with a blank Note, adding text to it, the main Edit menu considers this to be "Adding a Note", so if you wish to revert, ME offers you Undo "Add Note". This doesn't seem to work if you've already saved your Note. ME also offers Undo " Update Note", and Undo "Remove Note". If you've manually deleted all the text from your Note, ME considers this to have "removed" the Note, even though this term is ambiguous, since Notes can't be deleted ("cleared" would have been better). Remember too that ME's Undo applies only to the Active Thought, so if you make another Thought active, you can't expect ME to undo the Note of the previous Thought. Contrary to Darkstar's comments, I found that NE's Ctrl+Z was able to undo the changes made to the Note even after the Note was saved. However, the order of NE's Undo is also important. If you insert the text aaa bbb ccc in the following order: aaa bbb ccc then press Ctrl+Z, it will remove all three lines. If however you insert it as below: aaa ccc bbb Ctrl+Z will remove ccc first, then aaa and bbb the next time you press it. The bottom line is that I wouldn't use ME Undo on Notes at all.
PB 188.8.131.52 on Windows XP, J-1.6.0_17