Update Manager - E: Malformed line 54 in source list/etc/apt/sources.list (dist phrase), E: The list sources could not be read.

Thank you for taking the time to report this bug and helping to make Ubuntu better. This bug did not have a package associated with it, which is important for ensuring that it gets looked at by the proper developers. You can learn more about finding the right package at https://wiki.ubuntu.com/Bugs/FindRightPackage . I have classified this bug as a bug in update-manager.
For future reference you might be interested to know that a lot of applications have bug reporting functionality built in to them. This can be accessed via the Report a Problem option in the Help menu for the application with which you are having an issue. You can learn more about this feature at https://wiki.ubuntu.com/ReportingBugs.

Thank you for taking the time to report this issue and helping to make Ubuntu better. Examining the information you have given us, this does not appear to be a bug report so we are closing it and converting it to a question in the support tracker. We appreciate the difficulties you are facing, but it would make more sense to raise problems you are having in the support tracker at https://answers.launchpad.net/ubuntu if you are uncertain if they are bugs.