Jumpy Frame Rates

Hi,
For some reason now when I flyin FS2004 with the 2D panel the frame rates jump from 8 to 30 in little split seconds which makes it very difficult to fly as it is jumping around, if I go to the VC it gets smoother again. Anyone know why this might be? It dosen't just happen on one plane but most of them?
Thanks for any help.
For some reason now when I flyin FS2004 with the 2D panel the frame rates jump from 8 to 30 in little split seconds which makes it very difficult to fly as it is jumping around, if I go to the VC it gets smoother again. Anyone know why this might be? It dosen't just happen on one plane but most of them?
Thanks for any help.