Hi Johann,
My impression is, that routing on E/W borders doesn't work at all, but takes place at the basemap instead.
I've verified with two different start/destination pairs. Crossing borders in E/W takes only place, if roads in the basemap are available.
I have just tested a German map using mapsource and can route from W to E across a tile boundary from a place called Zedwitz to Trogen (a few Km) - it's crossing the boundary using a residential street. Also, the reverse route works as well. If I switch to the basemap in mapsource it just draws a straight line between the end points. Do your problems also occur in mapsource or just on the etrex? I shall now put the same map on my etrex and see if it routes across the boundary OK. Cheers, Mark