My sturdy and largely trouble-free Garmin 800 has suddenly gone blooey. When I plug it into my iMac, it doesn't go into data storage mode--that is, no icons
appear for Garmin and the SD card on the desktop. Instead, it begins to start up, acquire satellites, and get ready for a new ride.

After consulting the online owner's manual I discovered that if I hold down the reset button while the unit is turning on, the icons appear and synching can proceed. This works most of the time. But surely there must be a way to get it back to full, normal function?

All advice and suggestions welcome, and appreciated.

Try a hard reset. Before that be sure you copy all of your activities to your computer. You might want to take pictures of your screens so you can get them setup again after the reset.

I think I managed to bork my Mac by plugging in my mp3 player and then disconnecting it before ejecting it. My Edge 500 failed to show up on the desktop. But it went to charging (normal behavior) rather than the ride mode. I rebooted my Mac today and all is well again. You've rebooted?

I found google search to find a few useful threads on the garmin forums. I had problems a few months ago and followed the procedure to reset the device which fixed the problem.

1-800-800-1020

Garmin product support.