I go to commit a bunch of code, using Tortoise SVN, and it barks at me, telling me I can't do so without updating.
So, I update. It tells me that I am fully updated, having updated absolutely nothing.
Then, I re-commit the previous attempted commit and it commits as i there never was a problem.
Exactly what is being updated when nothing is being updated, causing the 'nothing to update' - 'need to update' warning to be thrown?
My understanding of this behavior is as follows:
It can be that a folder is seen by Subversion as out of date even though you just previously made commits in the same working copy. This happens because the revision information is stored per folder and not per working copy. Therefore it is possible that a sub folder has the head revision and you can even make commits (which will update the revision of that sub folder but not necessarily of the root folder of the working copy).
In this situation subversion only knows that the same folder in the repository has a higher revision and therefore it wants to update it. In some cases (as you described) the update will only change the revision information in the .svn folder.
I would use Clean-Up. If that doesn't work then I would try and save your progress and try to merge your changes into a fresh Check-Out version. The version you have chacked out probably lost some links along the way.
good luck!