MSDTC fails on Windows 2003 but security has been reset so its not that.

I am running SQL Server 2000 (clustered server) with Windows 2003. For some reason MSDTC is failing on distributed transactions. I can run code that begins and commits a transaction from query analyzer, or run a stored procedure from Query Analyzer with the same code in it and both work great, but if I call the stored procedure from a DTS job, then the job fails with the following error:

DTSStep_DTSExecuteSQLTask_1, Error = -2147217900 (80040E14) Error string: The operation could not be performed because the OLE DB provider 'MSDASQL' was unable to begin a distributed transaction. Error source: ..... Error string: OLE DB error trace [OLE/DB Provider 'MSDASQL' ITransactionJoin::JoinTransaction returned 0x8004d00a]. Error source: Microsoft OLE DB Provider for SQL Serve. The step failed.

Any help would be appreciated!Ensure MSDTC is started on the machine.
http://www.sql-server-performance.com/forum/topic.asp?TOPIC_ID=3451 for your reference.