I know it doesn't help get your screw out, but do yourself a favor and put M6x20 hex head screws and a flat washer in as a replacement. So many of the other screws use a 10mm socket, it will be like the rest. Just don't over torque them! I had the same problem with a stripped DISA screw, what a PITA (ended up drilling the head off, then it unscrewed by hand!)! No more issues.
Love my 330, until it breaks!