Problem:
A problem while opening the programm OptiSurface. The only thing he see is a black window. Is there a reason for that? (A screenshot was attached to the original ticket.)

Solution: 
It seems from the screenshots that the client was working with 2 screens. It could be related to that.  I run on two screens but if you drag the Optisruface window from one screen to the other, I have seen problems.

Try restarting PC running on a single screen and try again.  Also have they modified anything under Tools > Options Menu?  If they have unticked this and they have problems it indicates their graphics card hardware or drivers are not compatible with OptiSurface.  Disable Hardware Acceleration ticked ON is by default and is the safest option.