roscore fails to start after latest update? (precise, groovy, AMD64)

edit

I performed a update of my package based ROS installation yesterday (12.04, groovy, AMD64) and tried to start a roscore today, which results in the following output:

kohlbrecher@opstation:~$ roscore
WARNING: unable to configure logging. No log files will be generated
Checking log directory for disk usage. This may take awhile.
Press Ctrl-C to interrupt
Done checking log file disk usage. Usage is <1GB.

started roslaunch server http://opstation:32866/
ros_comm version 1.9.44

SUMMARY
========

PARAMETERS
 * /rosdistro
 * /rosversion

NODES

auto-starting new master
process[master]: started with pid [2686]
Traceback (most recent call last):
  File "/opt/ros/groovy/bin/rosmaster", line 35, in <module>
    rosmaster.rosmaster_main()
  File "/opt/ros/groovy/lib/python2.7/dist-packages/rosmaster/main.py", line 73, in rosmaster_main
    configure_logging()   
  File "/opt/ros/groovy/lib/python2.7/dist-packages/rosmaster/main.py", line 57, in configure_logging
    _log_filename = rosgraph.roslogging.configure_logging('rosmaster', logging.DEBUG, filename=filename)
  File "/opt/ros/groovy/lib/python2.7/dist-packages/rosgraph/roslogging.py", line 105, in configure_logging
    logging.config.fileConfig(config_file, disable_existing_loggers=False)
  File "/usr/lib/python2.7/logging/config.py", line 78, in fileConfig
    handlers = _install_handlers(cp, formatters)
  File "/usr/lib/python2.7/logging/config.py", line 153, in _install_handlers
    klass = _resolve(klass)
  File "/usr/lib/python2.7/logging/config.py", line 88, in _resolve
    found = __import__(used)
  File "/opt/ros/groovy/lib/python2.7/dist-packages/rospy/__init__.py", line 49, in <module>
    from .client import spin, myargv, init_node, \
  File "/opt/ros/groovy/lib/python2.7/dist-packages/rospy/client.py", line 59, in <module>
    import rospy.impl.init
  File "/opt/ros/groovy/lib/python2.7/dist-packages/rospy/impl/init.py", line 107, in <module>
    class RosStreamHandler(rosgraph.roslogging.RosStreamHandler):
AttributeError: 'module' object has no attribute 'RosStreamHandler'
[master] process has died [pid 2686, exit code 1, cmd rosmaster --core -p 11311 __log:=/home/kohlbrecher/.ros/log/e4297ce0-9d04-11e2-8192-9439e59a9133/master.log].
log file: /home/kohlbrecher/.ros/log/e4297ce0-9d04-11e2-8192-9439e59a9133/master*.log
ERROR: could not contact master [http://opstation:11311/]
[master] killing on exit

I also have fuerte installed and fuerte's roscore starts up fine.

I'm not aware of any changes on my part that could be responsible. OTOH I'd expect ROS Answers to be full of complaints if this happened to everyone. Any hints on how to solve the problems are appreciated.

/edit: Errors about 'module' having no 'RosStreamHandler' attribute also appear in other python code besides roscore (for the moment using the fuerte master with groovy nodes)