BB Bold 9700 :: Error Saving Memos And Disappearing Memo

I got the Bold 9700 from AT&T on Saturday and I have unlocked it and started using it on the Bell network as of yesterday. Before getting the Bell SIM card, I upgraded it to the latest OS from Bell (platform 5.1.0.116 ; app version: 5.0.0.423).I was taking notes on a memo, and I suddenly started getting an error saying "Memo updated externally. Changes will be lost and the viewer closed." I'm pretty used to saving on a regular basis, so I didn't lose too too much of my notes. It started saving OK for a while on the same note after it happened twice within about 5 attempted saves (so the 3 or so in between did work). At one point my memo got duplicated for some reason. I deleted it and was working with the one left. Eventually it started doing it every time I tried saving a note regardless as to whether or not I actually made any changes to it. Finally after not touching my BlackBerry for a while, the memo has disappeared. Not quite sure what's going on with my memos at this point. I haven't synced my BlackBerry with the computer at all today. I'm using BIS, and I have nothing that should be modifying my memos.

I am wondering if there is anything I can do or if I should downgrade back to AT&T's latest available OS version which is older than Bell's latest. I've found no one having these issues with memos, only with contacts and calendar entries. I've always used my BlackBerry for taking notes that are very important for me.