A user wrote me (and I guess this could be interesting for more mac users):
I have the program RouteconverterMac 1.23 in front of me, but where to search for a routeconverter.log file, and where is the user's temporary directory?
But I don't own a mac and don't know where the temporary directory is. Maybe its /tmp ? The file you need to search for is called "RouteConverter.log"
My mac laptop runs the 10.4.11 version.
I guess that's the reason why the embedded gpsbabel does not work for you: It has been compiled for 10.5.2. Try to find a 10.4 version of gpsbabel or compile gpsbabel for your OS version (http://www.google.de/search?q=gpsbabel+mac+os+x+10.4).
Then configure the path to the gpsbabel binary on the "Misc" tab of RouteConverter.