My wife's Vado did the same thing this AM. I assume it was contamination on the connectors since everything was fine after I blew off them off.
The Vado charger uses a magnetic connector for the charger. Works well, except I keep the chargers in the shop with the bikes in the Summer. The connectors tend to pick up debris off the shop floor (and anywhere else I lay them) from other pojects so each time I need to recharge I try to be sure to clean the magnetic connectors. Today it took a deeper cleaning than normal to get the charger 'red' (I'm charging) light to come on.