How to revive 2 xbees that won't connect via USB anymore?

Now 2 xbee s2 appear dead after reconfig from router AT to router API. USB failes to open. RX led blinks about 3 times and message box declared usb failed to open.
Have tried other working usbs. COM 6 (should be correct one) does blink one led the moment “read parameters” is used.
Other xbee on COM3 working just fine. Cables swapped no change.
Reset button held during power on, doesn’t help. One returned to seller. Exchange unit has worked as AT router for a week.
Windows 8.1.
Ideas how to reset?

Finally checked baud rate. Sure enough, it had changed to 1200 in the Bee. Able to read at 1200 then change back to 9600.
They are working again. Today however, it slipped back to 1200. It seems anytime I change config to Router API from Router AT, it crashes because it reconfigures its baudrate.