MAV when unlocking workstation

I did a lock workstation under Windows XP and when I unlocked the machine, I got a MAV error.

This happened in an executable version of my program so I went back into the IDE to re-create it. The same thing happened. The Debugger pointed to a simple line command.

Next I started a new program with nothing more than a line command. The MAV occured again after unlocking. Has anyone else experienced this?

Graphics 640,480,32,2
SetBuffer BackBuffer()

While KeyHit(1) = 0 
   Cls
   Line 100,100,300,300  
   Flip False   
Wend
End

This is in version 1.96.

i ran your code and it was fine. i'm pretty sure this has nothing to do with Blitz but to do with the OS itself.

I've had this as well in the past during different OS & blitz versions. My guess is that this has to do something with your graphics card. Ie. I've never had this when using proper cards like an nVidia, but on computer with dodgy Intel cards or other nameless cards the blitz screen would be blank or crash after unlocking or after returning from a screensaver!