Performance degradation with WPA hashes and Nvidia 331.20

[burst2]

I've been trying the new Nvidia driver 331.20 on a Linux with 3.12.5 kernel now. It looks like I'm constantly getting about half the amount of hashes I used to get with 319.60. Card is Geforce 780M.
I've tried several options and settings and none seem to have any effect.

Nvidia 319.60
Kernel 3.11.5
WPA2 ~42000 H/s

Nvidia 331.20
Kernel 3.12.5
WPA2 ~24000 H/s

I also tried the rest of the hashes and none seem to be affected, except the 2500.
Any help is much appreciated.