Problem loading UCCNC

[deckel11668]

UCCNC would not load on my workshop computer Windows 8.1 because the video was not adequate .
Following advice here and elsewhere I added a better video card along with the appropriate driver which permitted the soft ware to load ( but on a second attempt)

So I boot up the computer and when it has settled down I load UCCNC which appears to work but then after a short while the screen goes black ( and blank)
Then it lightens up and two messages appear.

"UCCNC has stopped working
A problem has caused the program to stop working correctly .Windows will close the program and notify you if a solution is available "

&

"Display driver stopped responding and has recovered
Display driver Nvidia Windows kernel mode driver version 451.67 stopped responding and has recovered "

So I click to close and try again . This time all opens up OK and works .
On one occasion I got a similar occurrence toward the end of an engraving routine but generally it will work until I end the session.

What I need to know is whether it is the computer , UCCNC software, video card , or driver ?

Any ideas where to go with this