Great that is good news. I run two of the 550 Ti's in SLI on my rig and everytime I update my cards. They at first seem to run ok then everything starts to act weird. Things don't want to work.
Video adaptors stop working, screen freezes, Internet Explorer stops working then recovers. Stuff like that so I have to take the drivers back to the 280.26. Then everything works just fine. Anyway just though I would share and good luck to you.