Happened to me this morning, but from what I can tell not many people where effected and the cause remains unknown but I think it was noting but a random issue as I haven't been able to replicate it since. If it happens again can you let us know because if it is something I want us to react fast.
It all depends on the time it happens. There is an automated backup that runs on the server. It is set for something like 3 or 4 AM EST. So the database could be giving out such errors during that time.
There was a few known bugs when we updated to the latest version of vB 3.8 which affected some options. Another one was the Mark All Posts Read. Since they were found Larry has applied the appropriate fixes and things should be close to normal now.
It doesnt matter if it is the first post, the last post or any post inbetween. As i said, it could be due to the backup script, it could have been due to an overflow of posts at that time. It could have just been vB acting like a idiot. We dont know exactly why the database errors come up when they do. We have looked into it and there is no full explanation as to why it happens. It just does. vB is of no help getting it resolved either.