Can't interact with certain Derma menus?

This issue has just randomly popped up, not sure why.
Basically, I’m unable to do ANYTHING with ANY Derma UI that stays on screen while I move (e.g. a DarkRP HUD, this is just an example).
While hovering my mouse above said UIs, the cursor flashes rapidly and sporadically. On Windows 8.1.

Can anyone please help me? This is really ruining my experience with a lot of gamemodes.

To clarify, interact would be scrolling, clicking, typing in, etc.

it might be an old addon that broke try turning off all addons