Acrobat XI is flicking sometimes.

Acrobat XI is flicking sometimes. Today is doing that. I have two pdf files open: A & B. A flicks when it is "active" (when I click to start editing it) and the B one doesn't flick at all in any moment (active or not active) A stops flicking when B is active.

I experienced this flicking thing once every 2-3 months, the problem is that it is bothersome to work like that and I can't figure out how to cure this problem.

I tried to close the A file but the flicking continue when I reopen it.

I am using windows 10.

Please help.

Thanks.