I know this is an old thread, but just wanted to let people know that you can get the audio all working again if you get this message.
Basically, you need to install an older version of the software which is available at: gawisp.com/Perry/zumo
Garmin will not help you with this, I'm sure they would rather you buy a new sat nav from them. Please don't let them know about the availability of these old software updates!
Here's what to do:
1. Remove any SD card from your Garmin (you have no doubt got most of your maps and mp3 music stored here).
2. Connect the 550 (or 500) to your PC.
3. SAVE a copy of the files into a separate folder on your PC in case it all goes wrong
4. Don't delete anything on your 550. Leave it connected.
6. Open the website
www.gawisp.com/Perry/zumo
7. Scroll down to the last available software update for your 550 and click on it to download.
8. Once down loaded, click on the file. It will start installing and prompt you when needed.
9. Once done (it will tell you) disconnect the 550.
10. Allow it to boot up (you may need to switch it on and off).
11. It will ask if you want to use the earlier software, select YES.
12. Reinstall you SD card and enjoy the restored voice prompts via the headphone socket or blueteeth once more.
If you have Garmin Express then ignore this if it fires up automatically. Better still, disable or delete it for now.
The downside is obviously you will have older software and any previous glitches this came with, but at least you now get voice prompts again. The maps are not affected of course.
Finally, plug the 550 back in with the SD card out and copy the remaining files as a backup.
It sounds long winded, and I'm no IT buff, but it's easy to do.
