My co-dev was working on revision 20858 which changed /App_Code/SQLCode.vb in our project (http://www.codeplex.com/micromanager/SourceControl/changeset/view/20858) As
you can see, that is changeset 20858. I had made a change in my local copy of SQLCode.vb. Instead of doing a merge (since my code was just testing a function), I reverted my changes. I then did an Update, which brought me to, according to VisualSVN, 20860!
That revision doesn't exist, and I am unable to pull down the changes the other dev made in 20858.
This is extremely frustrating and not the first time that I've encountered where I'm unable to pull down changes made by another dev, VisualSVN telling me the copy is up-to-date with a revision that hasn't even been made yet.