Catymag....I updated My 3790/34xx with webupdater to 4.40 without any problems, but it's a bit slow to load the new firmware
Yes, after downloading update on webupdater, unplugging and switching on the unit, the Garmin logo screen appears. Now after that the unit looks to be doing nothing.... be patient.
After a few minutes of static screen the 'loader' term appears at top of screen and the firmware load begins.
From there it is a few short minutes to finishing updating.
Another successful update here.