I am having the same problem with Bitstamp. I have made a sizable deposit which they have confirmed receiving, but will not give me access to it, and have started additional KYC even though I have already handed over personal details such as passport.
OrphanedGland and others, what type of amounts are we talking about here? It would be good to give at least rough amounts that got flagged for additional KYC so that others will know if they are likely to face the same issues when they deposit.