I have a G2X that I have recently been having card formatting issues. I lost my original 128mb card that I had used for years, so tried a 512 mb card for an event this spring. After that event I went to read the card on my Win 10 PC and windows gave a "Card Not Formatted" error. I tried again this weekend with a 256 mb card that I formatted on the PC prior to the event. After the event it again said "Card not Formatted".

I have not investigated any connections yet, but I was seeing the Satelite count bounce from 0-9 and speed was bouncing from 0-upwards of 200, and even showing negative 200.

I a new GPS antenna on order already (wanted to eliminate the magentic mounting and cable running across the roof, so have through hole hard mount dome antennas coming.