I have the same driver for the 285 and it does not run seemless. It takes too long to build the timeline.
So i am rolling one back which was just fine.
I have 280.26 installed as well and tried inserting a still into the timeline and have no problem whatsoever. It displays fine, both in the source monitor and in the timeline and program monitor when scrubbing. I suggest you do a complete fresh install of the video drivers, removing the old ones. I did not do that, but I had no problems. In your case, without knowing more details, a fresh install may solve your issues.
Thank you for pointing that out, and thanks to Ann for verifying that she's having an issue with it too.
That will help others. I always keep the last few drivers handy, just for cases like this. Going back a few years, nVidia had two drivers in a row, that caused issues for Adobe users, the trick was to roll-back to the last known good, and then wait. nVidia got a new driver out in about a month, and also had a settings workaround for the bad ones - in that case, there were some 3D StereoVision modules that were ON by default, and had to be manually turned OFF to get them to work.
Appreciated, and good luck,