Significant framerate drop while on ground

I need help!I've tested everything that I can think of and looked through the forums in search of a solution for this one:I am running FS9 on a P4/2.4, 1GB RAM, ATI 9500 Pro, Realtek On-board sound, Win XP, latest drivers for sound and graphics. Plus, I love flying in FS 2004. Framerates are locked to 20 and I get considerable good performance when taxiing on EDDF, which is my usual take off location. Now, whenever I fly somewhere else from there or following every plane crash, the performance drops down to between 1 and 2 frames per second while I (the plane) am on the ground with at least one wheel, strange. I thought that it might have to do with the fx effects and switched them off with the standard Cessna; no change. I have switched off generic traffic and get an approx. 2 frames/sec. improvement. I have landed the FDS Pilatus Porter float plane on the floats with retracted gears and it was very much better. Same thing with gears extracted and frames dropped again. Now, as soon as the plane is off the ground, frames rise to maximum again. Isn't that strange? I have no idea what could cause this. Maybe the FS internal control/following of the user plane while on the ground, if there is anything like that. Strange also that it does not happen when landing on (scraping) floats or on water. I am clueless and still considering going back to FS 2002 if I can't find a solution for this behaviour. Any suggestions? I'll be away for the weekend and therefore unable to answer or test before Monday next week. So don't take it as me being ignorant.A very frustrated Joerg