Just installed ubuntu and im having the same problem with software center. Also as with lazycat i couln't find that line in the file. This is what terminal returned to me:
2012-12-23 14:41:05,433 - softwarecenter
.ui.gtk3.app - INFO - setting up proxy 'None'
2012-12-23 14:41:05,583 - softwarecenter
.db.database - INFO - open() database: path=None use_axi=True use_agent=True
2012-12-23 14:41:20,912 - softwarecenter
ws - WARNING - Could not get usefulness from server, no username in config file
2012-12-23 14:41:21,478 - softwarecenter
.fixme - WARNING - logs to the root logger: '('/usr/lib/python2.7/dist-packages/gi/importer.py', 51, 'find_module')'
2012-12-23 14:41:21,478 - root - ERROR - Could not find any typelib for LaunchpadInteg
2012-12-23 14:41:24,765 - softwarecenter
.ui.gtk3.app - INFO - show_available
_packages: search_text is '', app is None.
2012-12-23 14:41:24,840 - softwarecenter
pl.aptcache - INFO - aptcache.open()
2012-12-23 14:41:48,755 - softwarecenter
.ui.gtk3.app - INFO - closing before the regular main loop was run
I used Ubuntu some time ago, but never that much so would really love some help on this