Try to use Catalyst 9.9. I don't know much about linux drivers but I had several problems with driver lock-ups under Vista64 related to memcopy routines (calResMap & calMemCopy). Also you can try to remove all memcopy to/from devices to check out if it's a reason.
In theory it's no problem to run multiple processes/threads with CAL. In practice you need to fight through CAL SDK and its bugs. I've finished with using only pinned memory when running multiple CAL devices.