I never encrypted my wallet.
you should try asking this question at bitcointalk.org. If there is a bug in the client then perhaps it will help if you try copying your wallet.dat somewhere and loading it into a new version of client or fresh install? It is a good idea to have your private key for each address you plan to store bitcoins in written down somewhere before you send bitcoins to them. You can then load that private key into any wallet in order to spend the bitcoins.