Comment 4 for bug 477670

Please backport this to Karmic, which has the same problem.

A workaround for users without updated ubuntu-dev-tools reading this bug report:

$ manage-credentials create -c ubuntu-dev-tools

This will launch your web browser, where you must login using your Launchpad user-id and password. Next you will be able to specify which access rights you want to grant to ubuntu-dev-tools.
Complete the process, and you will be then be able to use pull-lp-source normally.