After working for a week now heatpumpmonitor crashes after an hour

Hi,
I set up heatpumpmonitor on a Mac Mini, connected to a Tecalor 403SOL running 4.39. For a week everything worked, now suddenly heatpumpmonitor crashes after an hour:

Starting ...
========= Tue Jan 10 08:30:44 2012 =========
Error: the received getVersion response has an invalid length (53 instead of 2)
---------
Traceback (most recent call last):
  File "/usr/local/sbin/heatpumpMonitor.py", line 71, in doMonitor
    p = protocol.Protocol(config.getSerialDevice(), config.getProtocolVersionsDirectory(), config.getNewStyleSerialCommunication())
  File "/usr/local/sbin/protocol.py", line 112, in __init__
    self._version = self.versionQuery()
  File "/usr/local/sbin/protocol.py", line 250, in versionQuery
    return self._getVersion()
  File "/usr/local/sbin/protocol.py", line 232, in _getVersion
    return str(convert2Number(self._get("getVersion", GETVERSION, 2), 2))
  File "/usr/local/sbin/protocol.py", line 209, in _get
    raise IOError, "Error: the received %s response has an invalid length (%d instead of %d)" % (queryName, len(s) - 2, queryResponseLength)
IOError: Error: the received getVersion response has an invalid length (53 instead of 2)

=========
Starting ...
Heatpump reports Version 4.39
Using protocol definition from Robert Penz <email address hidden> and Jack Sleuters (Tested with LWZ 303/403 Sol, send me a line if it works on others too.)
Up and running
========= Tue Jan 10 09:45:23 2012 =========
Error: the received OperationalState response has an invalid length (53 instead of 10)
---------
Traceback (most recent call last):
  File "/usr/local/sbin/heatpumpMonitor.py", line 88, in doMonitor
    values = p.query()
  File "/usr/local/sbin/protocol.py", line 260, in query
    result.update(self._getValues(query))
  File "/usr/local/sbin/protocol.py", line 236, in _getValues
    s = self._get(queryData["name"], queryData["request"], queryData["responseLength"])
  File "/usr/local/sbin/protocol.py", line 209, in _get
    raise IOError, "Error: the received %s response has an invalid length (%d instead of %d)" % (queryName, len(s) - 2, queryResponseLength)
IOError: Error: the received OperationalState response has an invalid length (53 instead of 10)

=========

The only way to get it working again is to physically remove the serial cable after stopping the daemon, connect it again and restart the daemon. The graphs can be seen at wp.home.wiederhol.de.

Can you please help me figure this out? Also, it would be interesting for me to see the power consumption of my 403SOL in a graph.

Thanks in advance,
Thomas.