Thanks for the replies.
It's true that it could be a problem with my computer... I'd don't see what it'd be, but that's obviously a possibility and really, what do I know.
I've taken a screenshot of the edge of VisionLab and a small Internet window to compare. Here it is:
Slightly different, but that's a possibility as well.
As for VLab not running fullscreen, I've definitely checked in my preferences and it is
set at fullscreen. You'll also notice that the X to close the program is slightly cut as the annoying line slices through it.
Any other ideas?
P.S. I've been using VisionLab on this computer for about 6 months, now, and have only been experiencing this problem since the last week or so.