Can Bitcoin Wallets be fixed if they go funny?
They don't normally "go funny". You probably are seeing something that either isn't clear as to what is happening or you are encountering a symptom of some other problem.
Do I really have to unistall and reinstall and let it synch for another two days?
If you already have the blockchain downloaded, you can let bitcoin recreate a new wallet from scratch by removing the old wallet.dat.
Can I somehow retrieve the block data before doing this?
Keeping the existing blk*.dat and removing everything else will give you a clean slate with whatever blockchain you previously had.
There are alternative clients as well.
Electrum, for instance: http://ecdsa.org/electrum
is a lightweight client that does not need to download the blockchain