"MISSING SYNC MENU BAR - FILE IS BUSY"

I recently went to the Genius Bar to solve persistent wireless connection problems, and they suggested that I re-install Leopard. Since that reinstall, I get this message re the missing sync menu every time I restart.

My Internet and in particular Mail are barely working - long periods where they freeze with the color wheel circling. I am thinking that it must have something to do with this Sync Menu Bar message. Any suggestions re how I can fix that?
Thanks!
liz