Whenever I have a wait stats question, I look up Paul Randall's list: http://www.sqlskills.com/blogs/paul/wait-statistics-or-please-tell-me-where-it-hurts/
According to this page:
This is simply the thread waiting for a lock to be granted and indicates blocking problems. These could be caused by unwanted lock escalation or bad programming, but could also be from I/Os taking a long time causing locks to be held for longer than usual. Look at the resource associated with the lock using the DMV sys.dm_os_waiting_tasks. Don’t assume that locking is the root cause.
From using the DMV he mentions, you should be able to be able to determine the session and figure out what's in contention for the row.