After updating from Forceware 344.16 to both beta/whql 347.09 mid december and now whql 347.25 mid january I still have problems with 3Dmark11 to run with my GFX OC settings 
Sudden freezes and crashes back to desktop with 3Dmark11 GUI error or with Nvidia driver not responding. And sometimes my GFX OC'ed is totally reset to zero after a driver not responding message (GPU-Z report stock settings while MSI Afterburner show OC settings
), and when I then try to run 3Dmark11 again my cards run stock speed and then benchmark finishes fine
.
It's so weird after these 347.xx drivers 3Dmark11 is acting up when I run my cards with OC. With 344.16 there was nothing.
All my games CoD M2/3,BLOP 1/2, BF3, HomeFront, Wolfenstein etc and 3Dmark FireStrike (Normal, Extreme, 4K), Unigine Valley 1.0, Heaven 4.0 run 100% fine and stable for hours with my GFX OC and 0 errors.
Another quirck I noticed which is the same on my two PC's one with GTX 970 SLi and the other GTX 970 3 way SLi. With Forceware 344.16 my CPU score was around 13'500poins, but after 347.09 it plummeted to 11'990points. The 347.25 driver upped the score a bit to 12'500points. It doesn't make sense either.

Sudden freezes and crashes back to desktop with 3Dmark11 GUI error or with Nvidia driver not responding. And sometimes my GFX OC'ed is totally reset to zero after a driver not responding message (GPU-Z report stock settings while MSI Afterburner show OC settings


It's so weird after these 347.xx drivers 3Dmark11 is acting up when I run my cards with OC. With 344.16 there was nothing.
All my games CoD M2/3,BLOP 1/2, BF3, HomeFront, Wolfenstein etc and 3Dmark FireStrike (Normal, Extreme, 4K), Unigine Valley 1.0, Heaven 4.0 run 100% fine and stable for hours with my GFX OC and 0 errors.
Another quirck I noticed which is the same on my two PC's one with GTX 970 SLi and the other GTX 970 3 way SLi. With Forceware 344.16 my CPU score was around 13'500poins, but after 347.09 it plummeted to 11'990points. The 347.25 driver upped the score a bit to 12'500points. It doesn't make sense either.