What kind of account? (FB, Google, ???)
Have you gone to Settings->Accounts & Sync->(Account) and made sure the Sync Contacts box is checked? What happens if you click Sync Now here, do you see the sync circle popup go around and then disappear?
Also, August second is the day after ICS released... is this when you got it? Have you done a factory reset of your phone since you got ICS? If not, I would highly recommend it.