Thanks for reply.
I believe I have latest nvidia drivers but I'll check this evening. Actually is EVGA GTX550, rather than Nvidia GTX550, but I don't think that should make any difference
I checked using Eve, that has exactly the same problem. I also checked by starting Eve, getting the problem (this time looking like you are viewing everything through a faceted glass window, where each facet appeared to be textures used in starbase interiors), exiting Eve, then starting MO - the problem did not recur in MO - so it appears to be to do with card and/or drivers rather than the games. Sounds like the card not getting initialised properly?
My driver is 285.58 btw