Not working after reverting catalyst drivers

I was using the latest Catalyst, and noticed the warning not to use them, and noticed it was very slow compared to what I was expecting. So I reverted to Catalyst 13.1, and just to be sure I deleted the oclhashcat-plus directory and re-extracted, and rebooted.

Now it just refuses to work. If I run it on a valid hash (including the example commands) it unceremoniously dumps me out and tells me "oclHashcat-plus64.exe has stopped working". I'm using Windows 7 64 bit, the GPU is an AMD 6900 series, either 6950 or 6970 (can't seem to find out without opening the case and looking).

Thanks.