Electronics woes

Hi All, and thanks in advance for any help.

I have a Prusa Mendel using Gen6 deluxe electronics running Marlin v1 firmware. I am using pronterface on windows 8 with slicr.

I am now on my second Gen6 PCB and am unsure what is going on.

The situation is that I am able to successfully do a single test print with reasonably good quality. After the first print, however, the performance of the electronics seem to degrade rapidly. If i try to do another print it will typically appear to work and go through the motions, but will not extrude (pronterface gives a "heat limit reached, extruder turned off " error, even though temp is holding at 230, which worked perfectly minutes before with the test print).
After this second print the electronics will not respond correctly, and will only connect to pronterface intermittently. When it does, the motors can be manually moved correctly, and the temp and extruder can be manipulated, but if a print is attempted the printer will not respond at all.

When the electronics do not connect, they log the following error:

Traceback (most recent call last):
  File "pronterface.py", line 1566, in connect
  File "printcore.pyc", line 76, in connect
  File "serial\serialwin32.pyc", line 30, in __init__
  File "serial\serialutil.pyc", line 260, in __init__
  File "serial\serialwin32.pyc", line 56, in open
serial.serialutil.SerialException: could not open port COM5: [Error 5] Access is denied.
Exception in thread Thread-3:
Traceback (most recent call last):
  File "threading.pyc", line 532, in __bootstrap_inner
  File "threading.pyc", line 484, in run
  File "printcore.pyc", line 97, in _listen
  File "io.pyc", line 520, in readline
  File "serial\serialwin32.pyc", line 212, in read
ValueError: Attempting to use a port that is not open

Based on that, i have tried enabling and disabling COM5, but I really don't know why/how that port would randomly lock up, or how to stop it.

Because this is the second set of electronics I have tried that have behaved this way, I have to assume that it is my machine and not the electronics. One thing to note is that now whenever the printer is plugged in to usb, I can hear one or more motors move a little, just like a quick jolt. It does this regardless of if I can connect or not.

Tonight I am going to try and get an old XP laptop formatted to see if that helps, but I really do not have a clue what to do.

Once again, thanks for any advice you have.

not that this helps much but i too get an occasional "jolt" when connecting but am able to print with no problems. Maybe puts you mind a little at ease with part of your issue.

I use WIN 7 and dont have any issues with USB / comm ports. Will be interesting to see how you get on with XP

Good luck

Update: My XP machine seems to be permanently out of commission (electronics woes indeed), so i tried borrowing a friend's win7 machine to no avail. I can still not connect, but on this machine I do not even get a log message for why pronterface will not connect. Given the total lack of documentation on gen6 boards (let alone the "deluxe" version), it seems like i may be SOL.

Guess ill go buy a better documented board!