printer lost communications

I have been printing successfully for a couple of months now. every once in a while the print will stop or I cannot connect. but now It is constant. I can get it to connect sometimes for a minute or two then it will loose the connection.

I have not made any changes to my environment , I am printing from a laptop through a powered USB hub to the printer.

here are the logs below I keep getting this error before I lose connection
echo:Unknown command: ""

I have reinstalled the USB driver and have rebooted several times.
it almost seems like something is wrong with the printer circuit board.

thanks for any help
John

20:32:26.102 : echo: External Reset
20:32:26.102 : Marlin 1.0.0
20:32:26.102 : echo: Last Updated: Jul 22 2013 15:56:56 | Author: (none, default config)
20:32:26.102 : Compiled: Jul 22 2013
20:32:26.102 : echo: Free Memory: 5522 PlannerBufferBytes: 1232
20:32:26.367 : Error:0
20:32:26.367 : : Extruder switched off. MINTEMP triggered !
20:32:26.367 : Errorrinter stopped due to errors. Fix the error and use M999 to restart. (Temperature is reset. Set it after restarting)
20:32:26.601 : echo:Unknown command: ""
20:32:27.319 : FIRMWARE_NAME:Marlin V1; Sprinter/grbl mashup for gen6 FIRMWARE_URL:http://www.mendel-parts.com PROTOCOL_VERSION:1.0 MACHINE_TYPE:Mendel EXTRUDER_COUNT:1
20:32:30.018 : FIRMWARE_NAME:Marlin V1; Sprinter/grbl mashup for gen6 FIRMWARE_URL:http://www.mendel-parts.com PROTOCOL_VERSION:1.0 MACHINE_TYPE:Mendel EXTRUDER_COUNT:1
20:32:31.188 : Printer stopped due to errors. Fix the error and use M999 to restart. (Temperature is reset. Set it after restarting)

It starts off with a temp and then when it looses connection the temp is reset to 0 degrees.
then it will not reconnect. i can send the M999 command and it will raise the extruder .But I cannot manually move the extruder up/down left right etc.
I would think that the system would still allow you to move the extruder even if the heater is off.
when it was showing a temp I moved the wires around quite a bite and I could not make it short.

I have to reboot the PC and the printer several times to get it back. i am going to try another PC next.

Just tried a different PC and USB cable. same result.
must be something on the Robo. I cannot get the Robo to respond except for the M999 command.
the temp says 0 degrees.

any ideas ? bad circuit board?
open circuit ?

any ways to test ???