bump. anyone has a clue?

I am a gamer using his rig to mine when idle. About a year ago I was getting ~500Mhs using a Radeon HD7970, then because of a technical issue I stopped mining for a few months and eventually replaced the Radeon with GeForce GTX770...

...on which I am currently getting ~130Mhs.

What follows may be quite a dumb question: did anything change (eg some network property), that would explain a much lower hashrate on a better card? Or is there something wrong with my setup?

I'm using: BTCGuild/BitMinter, GUIMiner/BitMinter, Win7