yeah I figured my description might be confusing.
I'm graphic drivers are up to date (updated yesterday)
It's the C2 window which takes an odd shape, not the browser.
In the screenshot you can see a part of my desktop at the right hand side. And the bottom of the C2 window is missing because it's outside of the screen.
Seems like it has nothing to do with the preview browser window.
I've got the window maximized, then I minimize it (to the taskbar) and when I maximize it again it's ratio/resolution is screwed up.
In the previous post I stated that minimizing and maximizing solved the problem. I meant to say that 'restore' and then maximize fix the problem (in windows press the middle top corner button twice)
hope this clarifies the problem :P
EDIT: made the screenshot link clickable