Mercurial: Waiting for lock

In some rare cases, you get this error when pushing changes to a Mercurial repository:

$ hg push
pushing to D:\HgReps\Foobar
waiting for lock on repository D:\HgReps\Foobar held by ''
interrupted!

A few solutions to this problem:

• Figure out the process holding a lock onto the repository and kill it.

• If the above does not work, delete the file .hg/store/lock in the repository D:\HgReps\Foobar

Tried with: Mercurial 1.6 on Windows 7