The following links discuss this database error:
http://social.msdn.microsoft.com/Forums/en-US/sqldatabaseengine/thread/1901f6e1-2dc3-4763-874d-d5420345eb3f
http://blog.sqlauthority.com/2008/01/30/sql-server-fix-error-the-query-processor-could-not-start-the-necessary-thread-resources-for-parallel-query-execution/
One thing to try is to change the Max Degree of Parallelism in the SQL Servers Advanced Settings. SQL makes a parallel query plan at optimization time. Maybe not all of the processors were available or there were not enough threads available. Try setting MAXDOP to 2 or 3 to see if it helps. This can be done on Enterprise manager by right-clicking your server and go to the Properties item "MAX Degree of Parallelism."
