CHRIS K  One more thing with some Garmin units and some PC, virtual (on a MAC) or real beige boxes.

Make sure you connect your GPS to a USB port which is directly on a motherboard/logic board. USB hubs or USB's on expansion cards may not work.  
(Version 1.8)

CHRIS K  hi

If you ever wonder whether you can run Garmin's MapSource on Guest PC, the answer is - YES, YOU CAN.

PowerMac G5, Mac OSX Tiger, latest version, Guest PC 1.8, Windows XP SP2. I have uploaded City Navigator 7 into my Garmin Nuvi 350.

Here's how.

If you have Guest PC, make sure it's version 1.8, it supports USB ports for the first time.

Install MapSource, make sure to upgrade it to the latest version, download it from Garmin's website - that's important because MapSource doesn't recognize Nuvi - only the SD card in it's slot and the upload doesn't work. Also update your GPS unit firmware.

Connect your GPS receiver via USB port on your Mac - no serial adapters needed. Let your GPS register as an USB drive - be patient as it may take longer than on a PC. If you have SD card in your device, you should see two additional drives.

Once it's ready, you may start uploading the maps. However, it it will take much longer compared to a PC. Especially indexing files and building maps. Remember, this is emulation. However, transfer was rather quick.  
(Version 1.8)