What are your system specs/drivers?
I also had something similar happen in SHIII, and it was due to file corruption. If your specs/drivers are in order, it might be worth redownloading/reinstalling the game...
PS - I've not really been active lately on the Gamesquad forums (I'm Heinz Fischer there), but I've been lurking and really enjoyed the couple of threads you started about ships/campaign. Some cool info came out, so thanks for getting that discussion going
