With regard to the failed firmware 3.90 installation I contacted Garmin The Netherlands. Today I received an acknowledgement of the problem and they told me a upcoming new firmware release should solve the problem. So you're not alone with the issue, Garmin knows about it and promises to solve it "soon"
I provide the URL of the response http://www.garmin.nl/support/ticket/view/?...1500&s=o90n
Regards, Bart