I have a query that I have been running on a regular basis for several weeks now, and just tonight I got a page that the process that calls it had failed. I have narrowed down the problem to 1 specific part of the query, however I am about at my wits end trying to figure out the cause. Any help would be appreciated. Here is the offending query: SELECT * FROM ( SELECT a.Field1, a.Field2, b.Field2 AS Field3 FROM ViewOfLiveData a LEFT OUTER JOIN HistoryDataTable b ON (a.Field3 = b.Field2 AND a.Field1 = b.Field1) ) AS c INNER JOIN ViewOfLiveData d ON (d.Field1 = c.Field1 AND d.Field2 = c.Field2) And this is the error it returns: Server: Msg 8624, Level 16, State 13, Line 1 Internal SQL Server error. The subquery runs fine by itself. The error only occurs when I join it back to the view, and if I join to another table it works fine. As I mentioned earlier, the query has been running fine for several weeks, and we have been on sp3 this whole time. The only thing I know of that has been changed is that the latest security patch for that new worm that is going around was applied earlier today. I also checked our performance monitor trends and everything seems to be normal (i.e. no major fluctuations in anything recently). Anyone have any ideas?