>It's (obviously) intermittent. For sure, the second one was during a message update, the first one may have been as well. This seems to be borne out by some strings in the detailed error message.

Ok, thanks

>Also, since your complete switch to SQL Server the UT has been much snappier. During both of the errors I received, I noticed there was quite a long pause (est. 8 - 10 seconds) when nothing happened, then the errors came up. Most other actions (including some other successful message updates) seem to complete successfully in less than a second.

Yes, the hits are processed within 0.2 second in average. I need to find out what causes the delay in the transmission.