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
Tried with: Mercurial 1.6 on Windows 7