Garmin465t (suddenly goes off)

First
Tap your speed readout to get to the compass. Tap and hold the compass until the errorlog pops up, then exit the error log. When it pops up it creates a GarminError.xml file on GPS (mine is in the n:\Garmin\Diag folder) that you can copy along with the GarminDevice.xml file (in the n:\Garmin folder) and if you can locate it, a copy of the track during the time of the shutdown. Email them to Garmin's product support with a small description of the problem. I did this and they found a map error that was causing my shutdowns on my zumo 660. They forwarded the data to their R&D. (At least that's what they relayed back to me)

Second
Have you tried Garmin's WebUpdater software? It lets you update the firmware and afterwards, any other drivers for the chipset, voices, etc.

Third
Update the map even if you are at the latest.

The combination of these 3 helped my problem of regular shutdowns (sometimes 3 or 4 in a half hour) for a long while. After about a month I did have a single shutdown but none since.

This was what I did on my 2nd replacement zumo because the 1st one had the exact same problem. So far, knock on wood (a.k.a. my head), it is still working good.

As far as hardware Garmin GPS' are good, but software is a big problem since introduction 7x5 series and newer...that's the reason I decided to switch to different brand, when the time comes, I am sick and tired of software problems I had and I still have some with my 765T...in your case let the Garmin software support techs figure out...

I have 2 765Ts for my wife and daughter. Both are operating good. I always check the error logs in them when I update their POIs, software or maps. Neither of them are having any problems to talk about. Almost 2 years on one and 1.5 years on the other and their error have each have only 2 or 3 errors in their errorlogs.

My zumo 660 had the problems but since viewing the errorlog and updating everything as I said before it has only logged 2 errors and only had 1 shutdown. Thats a lot better than 4 or 5 in a half hour.