try to unload driver on smp-somputer and system gets bsod (in ExFreeMemoryWithTag), on uni-processor computer evererything is ok.
Probably syncronization problem…
but debuger gets that ExFreeMemoryWithTag couses BAD_POOL_CALLER
Memory was already released or your memory pointer was corrupted. Put the breakpoint on the pointer access and trace all operations with it during your driver unload.