I remember someone else had this problem recently but it was resolved after getting a new blockchain or something like that. [Update: Read luke-jr's suggestion first.]
It wouldn't hurt to try starting the client with -rescan.
If that doesn't fix it, try removing the blk*.dat from your data directory and restart.
Or, for testing purposes a quicker method to get a copy of the blockchain is to download a recent blockchain binary download:
As far as importing into a new wallet, v0.6.x as importprivkey: