Hmm, it's more than a year since I used GV, so can't remember what menu options it might have, e.g. whether there might be one to set the default behaviour when connected - I believe the stock ROM has this, the one I'm using now does not. Have you got USB debugging enabled? That's just a guess, by the way, but as it's another thing that you might use USB for it might be that behaviour differs if this is enabled/disabled (I always enable it anyway).