when I mean "too fast", the other characters seem to fly through the room- I notice them and they are gone allready!
Interesting. Never seen it in Q3, but it did happen to me in Unreal Tournament. I bought a new (much more powerful) video card and suddenly my FPS went up to something 300 or over, and everything (including me) moved much faster than before. The worst thing was that it was location dependent (i.e. in large rooms where there were lots of things to render it slowed down, then in narrow corridors it went like crazy again). Totally unplayable. UT does not have FPS capping so there was nothing else to do but crank up quality until the FPS dropped to acceptable levels. Never had thought I would try to lower my FPS :-)
Conclusion: try to cap your FPS (com_maxfps "125") and increase resolution and/or texture details. May help.