Perform the following tasks to alleviate the problem:
Locate the transaction that is holding the lock on the required resource, if possible. Use sys.dm_os_waiting_tasks and sys.dm_tran_locks dynamic management views.
If the transaction is still holding the lock, terminate that transaction if appropriate.
Execute the query again.
If this error occurs frequently change the lock time-out period or modify the offending transactions so that they hold the lock for less time.