Sounds like your problems had nothing to do with the wifi card upgrade, or the wifi connection at all. I'd say it's pretty conclusive, you were flying in an inappropriate area surrounded by tall trees and skyscrapers and most likely near the edge of a 3000 foot cliff that blocked most of the sky. I know you said you were 300 feet up with no obstructions, but I'm telling you that you were surrounded by obstructions. I actually suspect you were flying indoors... no, you were in a cave. No wonder you lost GPS. Pretty much case closed... and don't bother to question my conclusion, because I'll deny every word of it while sticking to my story word for word!
But back to reality... it would be interesting to test the GPS in U-Center with the stock and aftermarket wifi cards. See if there's a decrease in sat reception strength with the replacement card. Maybe it's putting out more interference. Just a thought, but usually when a change is made and other things start acting up, it often has something to do with the change that was made...
If it looses GPS, it should switch to manual immediately. But loosing GPS isn't always, or even often, an on/off kinda thing. The quality of the fix starts to degrade, which can effect the flight, and when it reaches whatever threshold determines an acceptable lock, it could bounce around, dropping and regaining a (minimally acceptable) lock. So, as with most auto-type modes, the pilot should be ready to manually switch to manual and take control, as opposed to waiting for the computer to do it.
