Update manager error: Comment=Flock not known on line 3 source list/etc/apt/sources./list, E: the sources could not be read

When I try to open the the update manager I get the following error message:

An unresolvable problem occurred while initialising the package information.

Please report this bug against the 'update-manager' package and include the following error message:

'E:Type ‘Comment=Flock’ is not known on line 3 in source list /etc/apt/sources.list, E:The list of sources could not be read.'

When I go Synaptic manager I get the following message:

 E: Type ‘Comment=Flock’ is not known on line 3 in source list /etc/apt/sources.list
E: The list of sources could not be read.
Go to the repository dialogue to correct the problem.
E: _cache->open() failed, please report.

When I go to Add/Remove Applications I get the following:

Failed to check for installed and available applications

This is a major failure of your software management system. Please check for broken packages with synaptic, check the file permissions and correctness of the file '/etc/apt/sources.list' and reload the software information with: 'sudo apt-get update' and 'sudo apt-get install -f'.

Any assistance in resolving this would be greatly appreciated.