Here's a very crud way for solving the problem once in a while.

exec sp_who2

Look at the blocked by column. That will list the spid that is most likely blocking everyone else.

then run KILL <put spid here>.

Then rerun sp_who2 again to see if the lock is resolved. Sometimes you need to do this 2-3 times.

This stops the immediate problem but it doesn't prevent it from happenning again.

Also keep in mind that all the transations that were running need to be restarted.