I have updated my wallet to version 0.603 of bitcoin, and it works, however that version of bitcoin is very unstable, and crashes frequently, I have used version 0.502 and it is very stable.

The problem is that my wallet will not work with version 0.502 now that it has been used with version 0.603.

Any recommendations on how to migrate the wallet from version 0.603 to version 0.502?
Moving the bitcoins is simple, but how do I move the keys, or migrate the wallet to the older version?