Worth a try but Quentin D's 1-800 number indicates he's in the US of A.
The impression I got speaking to Garmin UK was that they've been telling the US that there is a problem for a couple of months but the US didn't accept there was an issue until recently.
Fact remains that the two I upgraded did not shut down prior to the upgrade but did afterwards. Unfortunately I'm groundbound at the moment until we complete the Permit renewal so I won't be able to confirm whether the rollback to 4.1 fixed it.
I'd be interested to hear if this reset works, i.e. someone has the problem, cures it by the reset and it doesn't come back.
Mike