Android - Why has my Android phone stop updating calendars, mail etc?
Settings -> Accounts and sync:
- Ensure Auto-sync is checked.
- Check the relevant accounts to see if sync is enabled for them (click the account and see what's checked off).
Another possible cause: is your phone's memory full? If your phone is low on free memory, it will not sync any new data to it. You'll have to uninstall some apps or move them to the SD card to resolve this.