Other than the obvious lose cable connection, the only things I can think of are possibly refresh rates on the LCD monitor, these may have been reset to an improper Hz rating when u installed the new card/drivers).
What resolution and refresh rates are you using on the LCD? Also what model # etc for the LCD.
The blinking, is it like a 1/4 sec blink, almost like a flicker, or is it like a LCD turns off, 1-2 seconds later it turns back on?