This has happened when I flashed to RC1 and RC2 and ended up restoring because i couldn't for the life of me get my gmail to sync or do anything. Each time I flashed to one of the CM6 builds, after the installation when i launch my gmail app it goes to a screen that says:
"Waiting for Sync. This account is not setup to automatically sync. Press menu->refresh to sync this one time or go to accounts & sync and setup gmail to sync automatically."
The first time i saw this i said no big deal and tried the menu->refresh option just to check my mail. Well nothing happened, and then when i tried to go to accounts & sync to add my gmail account I don't even get the option to add my gmail account. Next i went to manage applications and cleared the data for gmail and gmail storage to try to reactivate my account and unfortunately I can't do this either, gmail wouldn't even open after this. It just opens and closes instantly.
I've flashed back to 5.0.8 and everything is good, but i really want a froyo build that actually has a functional gmail. Hopefully someone has experienced the same problem and can provide a fix.
Thanks in advance.