What menu extras do you have installed?
I found that after I upgraded to Tiger, several menu extras became awfully flakey. GmailStatus in particular started hanging at seemingly random times (I've since replace it with Gee), and there were a couple others, like Butler, that needes to be updated.
The only advice I can give is to uninstall and re-install the problematic menu extras. If that doesn't work, I'd start looking for alternatives.
But again, it'd help to know exactly which menu extras you're using. Also, how long have you been using Tiger? Did this problem begin shortly after upgrading from Panther, or did it just pop up out of the blue?
