The first thing to look at if you get any errors is the version of you driver. Be sure that you have the latest one for your GPU.
If you get the following:
ERROR: clGetPlatformIDs() -1001
your GPU probably isn't supported.
to be continued..
I'm proud to announce that hashcat is now a part of Backtrack, Archlinux and Slackware.
Congratz Atom!