This may happen at other times too, but I noticed that the parse button of sidekick stops working after I change projects in the projectviewer.
When this happens, I usually notice a line like this in the activity log:
[error] String: build.xml (/home/ezust/jedit/trunk/)
[where this is the file I was editing].
I'm not sure where this message is coming from.
Logged In: YES
user_id=935841
Originator: YES
got it working via a workaround.