This any help Dids. ?
You beat me to it..... The following was my contribution to that thread....
First connect and switch on the eTrex. Once the eTrex has booted up, using Control Panel, open up Device Manager, look at all the options for USB and Serial Port Comms.
It should tell you what port the eTrex is using. With the eTrex still on and connected, once you've identified the port, open Memory Map, click on the GPS tab onthe MM drop down menus, then select GPS Setup.
Once you've opened the setup menu, check what port MM is looking for the eTrex in and change as necessary to the port that Windows has selected.