When I acquired my 2940, I thought it was broken, for I too had hangs.
I found out that while the 2940 is busmastering (which I knew) the IDE
on my motherboard was trying to cache.  Thus, at some point whilst
using IDE and SCSI, the caches would fight, and the machine would lock
solid.  Almost lost all my files this way.  Check for IDE Prefetch Buffers
in your BIOS.  (SIS's 5x86 motherboard?  PVI-486?)