When you plug in the USB cable from the 550 to the PC, the 550 automatically goes into a "USB-connected mode", by rebooting. The graphic shows a stylised Zumo connected to a PC, and then it starts saving routes, track logs etc. for transfer to the PC. You can safely cancel this step if you're not getting trip data from the Zumo. If your Zumo does not go into PC mode then I'd be inclined to
1. try a different USB cable
2. re-install the Mapsource program and USB drivers
3. if none of the above work then a call to Garmin.
BTW, it is possible to write routes created on the PC direct to the SD card (via a card reader). Have a search on here or the Zumoforums.com for more details.