MartinK: I did not put them in a subfolder, no. Figures I should've tried that. The GPX tracks do show up when put in a subfolder.

However, I still have the problem that they don't load properly... I have tried several different ones to try to figure out what could be wrong:

GPX tracks exported from ArcGIS - which is the Gold Standard when it comes to mapping software - will load, but modRana loads them incompletely. For instance, a gpx made up of several tracks will only display the track points and segments within the first <trk></trk> handle. Subsequent <trk> entries are ignored. If you want to take a look at it, I have attached an example of such a GPX file containing several tracks, where only the 3 points within the first track are loaded by modRana, but where ArcGIS, Google Maps and Mappero on the N900 all load the entire file. (It was too long to put in CODE tags, and I had to zip it to avoid "invalid file" message.)

On a side note, GPX files saved by Mappero will simply give a "loading tracklog failed" message. I would think this to be Mappero's fault, if it wasn't for the fact that I can accurately import Mappero gpx-tracks into ArcGIS or Google Maps without problem.

In fact, all my GPX tracks will display properly in Mappero, and their KML equivalents display properly in Marble.

I'm available if you want me to run some tests on your behalf.