They are down because they were hosted on Linode.

However, we closed the TH withdrawals
and that means ....

were funds lost to the linode hack?
Let me be clear, Bitinstant is
not TradeHill. We simply offered the means to move your USD out for a 2 week period. Everyone who request the withdrawal via Bitinstant recieved their funds within 24 hours or so.
Although I doubt your funds were lost (Why would you be keeping it in TradeHill when they closed over 3 weeks ago?) You should be contacting TradeHill.