#12 random editing freeze on note

[Brunello Ivan]

when opening pnotes, all notes are editable.
After a couple of minutes, editing behaviour seems unreliable:
- i can move notes around
- i can create new notes
- I can't roll/unroll notes
- I can't edit them.

This happens expecially on long notes.
I have a total of 5 notes currently on my desktop.