I've been a dedicated Tomtom convert for 5+ years, but since its not available on the storm yet, I downloaded the 7 day free trial version from Garmin: full version is £60, before 20% bb lounge discount.

Tried it once...not happy with a few things. The maps weren't detailed enough (I like to know where the rat runs are) and it had a crazy route in mind for my daily commute.

I was going to give it another go but now it has an error message at startup: "unable to authenticate" and after retry: "unable to fullfill request. please try again later. (code:99502-051)"

According to a very unsure person at Garmin the software doesn't like 3g? and it runs better on gprs?
How do I chose what connection method an application uses?
I can't believe this is the problem though.

i have been using tomtom and recently navingo on my touch diamond... they were awesome... i tried garmin for 1 day before buying it.

Why? free traffic for life... This app has saved me 6 hours of traffic in the past two weeks. Worth every penny. Might not be as fancy as the rest, but it works and reroutes instantly when traffic is detected.

I have garmin mobile for navigating but if I want map details I use google maps. The two apps are built for different purposes.

I have seen the "unable to fullfill..." error even on VZW. It happens when you start Garmin Mobile in an area without data service, your Garmin sw can't authenticate to the garmin servers. At least this happened to me when I was in an area that didn't have data service.

I've heard that the Handango version doesn't authenticate the same way. Perhaps you should try their trial to see if the issue resolves?

I've experienced this too many times now and I think I have worked out why it happens - in my case at least. The aggrivating thing is that i only got it working again yesterday!
If you select the Garmin shortcut from the screen (accidentaly or otherwise) and then try to cancel the selection before the program boots, it kills the application and will not then connect to the server the next time you try and start it.
If you have not already done so, you will need to call the Garmin helpdesk who will then send you a link to download the app again to reinstal it. It is best to reboot the unit before doing this (remove/replace battery) to prevent it from crashing half way through.
If like me you have the Garmin shortcut on the front screen of the handset you are more likely to accidentally select it so I have moved Garmin to the Application folder. A bit of a pain but much less painful than having to get it back to just how it was before you killed it.
I have shared this with Garmin today, whilst it is no good for getting it working again it may help you prevent it happening again.
Adam