Are you resynchronizing the client? I find that my client doesn't want to connect to peers if I don't completely delete the data directory after a corrupted block. If you want to try, you can try deleting the data directory after backing up your wallet.dat first.

When you try to resync the client, disable anything that could probe your Bitcoin related files for the moment. If possible, try to create an exclusion for the directory. It is possible that your programs was the source of the corruption.