A colleague of mine had problems updating his sources. We update the folder and it looks like it's updating to the latest revision. ("updated to revision xxxx") Then, we check the log ("Show log") for some files -and the folder itself!- and we notice the update process didn't work properly. Several files are updated to a different revision two weeks ago, etc. Files with revisions older than 17/12 are all up to date, files with newer revisions only have been updated to revisions up to 17/12. In the explorer, the files have the green 'check', indicating the file is up to date.
Based on my experience with SVN, fastest possible solution for you would be to perform a clean update, but only in case you don't have any pending changes to commit. You might have corrupted the repository by an accident or something like that, and SVN does not know how to handle certain files in your local repo.
Hope this helped.