Well, I kind of have the same issue, but with different cards. 285.62 was solid as a rock. I went against my own advice and updated to 295.73 (nothing's broke, don't fix it) and can't get a solid run for the life of me. 296.10 do not fix this issue, but retrieving 285.62 from the recycle bin does.
I swept the home that day so this is on GTS250's, 260's, a 460, 470, and 560Ti's. What the 296.10 did get back to life was the single GTX 570 which I just shut off out of frustration. What happens with me is not just WU's not finishing and doing the 24hr timeout, but the driver crashing with just about any video streaming done on them even when not folding.
I haven't had a minute to play with them, but it's just ironic that I'm being shored up by a pair of underpowered AMD cards to keep my PPD from being zero. The ironic part is that AMD drivers are sucky and I can't get nVidia's to do basic functions. The 460 even crashes in Minecraft now...something's wrong with the drivers or the Cuda load. Can't fold trouble free for years with this stuff and point to anything else but what's changed...drivers.