success after days of trying
For four days I tried to make it work with Panther with both USB (2.0) and two different serial port adapters. I nearly bought a PC.
Mapsource would find my 276C but would not load it with the maps. I tried numerous settings, speeds, configurations, and even USB but never loaded anything.
Finally I went back to my old Ti G4 Powerbook and started up in 9.2.2 (NOT running classis in background but booting from the old OS) and in one try the program found the GPS and loaded 219MB of maps. It took about 1.5 hours.
Could be the USB 1.0 vs USB 2.0 but many have had more success with OS 9.x.
I'm running Virtual PC 6.1 and Windows 2000.
Hope this helps.