I have noticed when I use my dual monitpr gtx560 ti card that PP5.5 playsback a lil strange.
When I choose a spot on the timeine to start play from the footage looks like it goes backwards for a second then starts sometimes. Seems like it started when I enadbled dual monitors. Must also say I played hell trying to get the right monitor to let me move the desktop start and icons to the left computer. I could not get it to move to the right side. I had to unplug the right monitor and restart with one monitor then plug in the second screen (right) after windows was up and running. That was weird.
Any Ideas I am open ears.