Similar problem here
(Using CM 5.0.8 final on my original black G1)
I can manually sync with the server to get email, but syncing seems to happen maybe once a day for the past week or so. It used to happen so frequently that i'd see email on my phone before i'd see it in my web browser if i was at a computer.
Haven't changed anything recently... Tried rebooting the phone of course.
Can't find the tool for clearing out gmail on my phone, so i haven't tried that.
any other theories?
Edit: Turned off sync everywhere and rebooted. Got stuck in a boot loop.
Used amon ra recovery console to wipe dalvik cache
Boot loop is fixed
Refresh problem seems fixed too.
Current Phone: Stock t-mo G2.
Former phone: original BLACK G1, CM 5.0.8 Danger SPL, gapps-ds-ERE36B-signed, recovery-RA-dream-v1.7.0, Radio 2.22.23.02, Swapper2 ->512mb SWAP partition 60 swappiness. See no need to root yet....