[dba-Tech] Display Turns Sideways

Dear List:
 
Just got a call from a customer with a problem I've never heard of before -
the image on his display is rotated 90 degrees.  
 
They leave the computers on all night.  When he came in this morning, the
image was rotated.  He tried to power down normally, but he did not get the
shutdown dialog box after clicking Start, Turn Off Computer.  So he powered
down using the power button.
 
Rebooted, and the display was still rotated 90 degrees.
 
We checked first to see 1) that he wasn't laying down, and 2) that the
bottom of the display was still  resting on the desk. Both checked out OK.
 
The machine with the problem is hosting the back end of an application I
developed for them.  And they are getting the 'Disk or network error'
message intermittently.  So there may be a NIC problem.  But I don't know
how the display problem could be related. (which says more about my hardware
knowledge than the problem)
 
Of course, he didn't change anything.  Any ideas, anybody?
 
MTIA,
 
Rocky