We have just figured out there is an undocumented 2 MB file size limit for the map. Could that explain your trouble?
Ah yes, that would explain it...
Yeah, I never got it to work directly on the website but if I publish using quickroute then it's fine. But you need a gps track to use quickroute so I just pick a random one and make it invisible.
The web interface upload should work if the file size is under 2 MB.