Hi Steven,
Is it the same USB TinyShield used in both cases? If so, make sure the connector between the USB TinyShield at the processor board are well connected. If it continues, I'd suspect that there is an issue on the TinyDuino processor board with the connection. If so, we'll replace this board and get you out a new one, just email me directly at kburns@tiny-circuits.com and let me know.
Thanks,
Ken Burns
TinyCircuits