Troubleshooting Google Sync on Android

Having problems with Google sync on your Android (1.5) device?

Try this:

Press your device’s < Home > button, then press < Menu >.
Select Settings.
Select Applications, then Manage applications.
Select Gmail Storage.
Note: If you don’t see ‘Gmail Storage,’ press < Menu > again, then select Filter > All.
Select Clear data. Answer OK when prompted.
Return to the list of applications by pressing the < Back > button on your device.
Select Gmail and then select Clear data. Answer OK when prompted.
To restart your device, press and hold the < Power > or < End call > button, then select Power off. Press the < Power > or < End call > button to power on.
Your device will re-sync with the server after restarting (this may take several minutes).

If the above steps don’t resolve the issue, check to see if you have any account notifications on your device.
Press your device’s < Home > button, then press < Menu >. Select Notifications. If you have any system notifications about a sign-in or password error, you should make sure your account information is correct in order for Gmail to sync.

Info taken straight from Google:

http://www.google.com/support/mobile/bin/answer.py?answer=113869

Worked a treat for me.

Simonthegeek