Does it behave differently in TE or Campaign modes? Or do you only fly instant action. I assume it wasn't behaving like this with your previous version of Windows.

Would be worth your time to have a look just to see if all modes are effected or not. Instant Action has been in a sort of broken state for a long time,
and BMS team makes no efforts for improvements here. You could try installing in Win7 compatibility mode. Run as Admin.

4.33 is no longer supported since the release of 4.34 so you probably won't get much help over at the BMS forums, but nothing ventured...nothing gained.

Hope you get it sorted!