Crack(?) at the corner of the window.

[tonydw96]

I wonder what's the cause of this

it's like a crack, but i don't really know what is it
any chance I can solve it?
Thanks

 

[BisVal]

Try changing the theme and see if it's still there.

 

[gregrocker]

It looks like pixelization, perhaps having to do with the specified Screen Resolution.

Try updating your Display driver.

Then try different Screen Res to see how it affects it.