What are you trying to do with it? Does a crossover store a tracklog (breadcrumb trail) in the GPS that can be downloaded?
I assume it hooks up by USB cable, is that right?
If so, you don't get the GPS to communicate (eXplorist style), you just open the drive that comes up under windows and copy the files, which TopoFusion can read.
If you're trying to do live tracking / moving map, you need to set it to Magellan/NMEA and make sure the baud rate is correct, probably 4800 baud.
Hope that helps, if not feel free to ask more.