Computer black screen crash with LAN shared file access

Access to shared files (jpeg digital photos) from another homegroup computer causes my computer to crash. The screen turns black, all disk activity stops, computer power light stays on, but there is no response to input devices.

The event log shows only an Event ID 6008 Source: EventLog "The previous system shutdown at 12:14:25 PM on ‎7/‎11/‎2013 was unexpected" logged after the power recycle/reboot with the time of the black screen (rather than the reboot time) and Event ID: 41 Source: Kernel Power "The system has rebooted without cleanly shutting down first. This error could be caused if the system stopped responding, crashed, or lost power unexpectedly." Generally nothing at all in the System or Application logs for 5+ minutes prior to crash.

Action Center history shows no Windows failure, under "Misc Failures" the problem is described as "Windows was not properly shutdown" (Duh!)

Seems to happen every time trying to use Windows Preview to look at files across the LAN. Both computers are Windows 7, both up to date. I have run chkdsk on all disks recently. File sharing has worked OK (barring various annoying network configuration issues) until this recent repeatable problem.