Win 7 blk screen crash using external dirves?

I have all my photo files stored on external drives in Burly enclosures. My working files are on a drive plugged into an eSATA port, which is generally trouble free when it and a USB drive are the only ones turned on.

Older archive drives can be turned on using a 4 bay Burly enclosure via firewire 400 (Burley 4bay with port multiplier). All these are single drives, not RAID. At times, browsing these files, with Photomechanic or Bridge, the pc will lock up and crash with the attached black screen.

After rebooting, after a slow start, things seem to recover.

Has anyone seen something similar? Any suggestions? I am thinking about giving up on the Burly 4bay enclosure, which in the past (with xp) was my primary external drive system.

I appreciate any suggestions, John