We had the whole development environment down for a day. After spending a good bit of time debugging, we discovered that we were getting a significant number of errors in our event logs saying:
Inner: The transaction has aborted.
Inner: Failure while attempting to promote transaction.
Inner: Fatal error 8510 occurred at Aug 5 2009 1:09PM. Note the error and time, and contact your system administrator.
A severe error occurred on the current command. The results, if any, should be discarded.
They were thrown against the running of several different stored procs and because of the architecture of our system, all of our COM+ components were rendered useless.
I found a post that talks about 'fatal error 8510' that was interesting:
http://blogs.msdn.com/asiatech/default.aspx - go to the bottom of the page (it's a ways down). However that turned out to NOT be the resolution to our problem
The resolution to our problem resided in the fact that SQL Server could not initiate a distributed transaction. We had thought that there was a problem with the MSDTC cluster, but that turned out to not be an issue as other sql servers in the cluster could initiate distributed transactions. Restarting services on the sql server that could not initiate distributed transactions resolved the problem