I would not say it is 'normal' behavior per se , but I believe it ties to the fact that starting with Windows Vista (and continuing into Windows 7) the NTFS (The filesystem your hard drive gets formatted to to run Windows) is now a transactional file system. This means that changes to the file system are not committed into being 'real' until all changes are completed and it is like a switch making all changes appear at once. This is the first actual production use of a transactional filesystem, so this is where my finger is pointed, albeit a very 'cool' and useful technique, there are glitches like this showing up.
My suggestion to you would be to run a complete disk check and hopefully that will get everything back into sync and refreshing properly.
"start button" -> "computer" -> right click "C:\" drive -> "propertied" -> "tools" tab -> "check now.." -> make sure "automatically fix filesystem errors" is checked
you will have to "schedule" it and restart your computer and let it do the work.