Graphics problem - 'fish eye perspective'

[siege]

I've been using FMS beta 7 ok (using DirectX v7) until recently when I installed a new game from a CD which prompted me to install DirectX v8 (which I did): FMS now occasionally displays a weird 'fish eye' perspective appearance. My system is :- Windows ME, AMD Athlon processor, 192Mb ram, graphics Nvidia TNT2