This time I captured the gpx File with TrekBuddy.

I already had tried the software some weeks ago and didn't really like it back then, but Hanno B√ɬ∂ck told me about it when I asked him about j2me gpx logging software. So I tried it again and what can I say… the UI is imho worse than SportsTracker, but somehow the results seem to be better :)
This time I had the slider of my N95 open though.

I'll do some more testing when it isn't raining :-/

p.s. TrekBuddy is supporting the j2me Location API (JSR-179) which can access the internal GPS of the Nokia N95