9.1-R and garbage on the console

[bsd at lavabit.com]

Hello.

I installed 9.1-R amd64 on a flash drive and boot off it to do remote ZFS
backups.  Booting and the text console screen, including the other alt-f?
consoles, work fine at this point.  A few minutes into the ZFS receive my
console turns into blocky garbage:  http://imgur.com/y8kWR . The system is
not crashed and works fine via SSH.  The box's mainboard (GA-E7AUM-DS2H)
has "Integrated NVIDIA GeForce 9400" graphics.  It appears to me that the
RAM shared with the video card is overwritten/corrupted.

Any ideas on how to remedy this?  Thanks for any advice.