D, I think I've narrowed it down to either a bad slot on the double micro SD reader in my Helix 9 or a bad micro SDcard. I keep my Zero lines map card in one slot and a blank card in the other.
I took a short trip Wednesday night (got blown off the water by the wind!) and without the blank card in the right hand slot things worked just fine.
Next time out hopefully I'll have a new blank card to plug in to see if gives me trouble or if it's the slot itself.