If you're willing to uninstall all your applications (as you've demonstrated), then perhaps you'd be willing to also wipe out your maemo-mapper configuration in hopes of solving the problem.

First, uninstall maemo-mapper. Then, from an xterm, run the following commands:

Then, reinstall maemo-mapper and start it up. It should give you the whole "first time running maemo-mapper" bit. Set up your receiver and your repositories, then try downloading your route again.

If that doesn't work, write down the exact error message and tell me what it is. It might be a firewall problem. Is your N800 connecting to the same network that you used to test your route through http://www.gnuite.com/cgi-bin/gpx.cgi ? Any special proxy settings?