If a Subversion command cannot complete successfully, perhaps due to server problems, your working copy can be left in an inconsistent state. In that case you need to use TortoiseSVNCleanup on the folder. It is a good idea to do this at the top level of the working copy.

Cleanup has another useful side effect. If a file date changes but its content doesn't, Subversion cannot tell whether it has really changed except by doing a byte-by-byte comparison with the pristine copy. If you have a lot of files in this state it makes acquiring status very slow, which will make many dialogs slow to respond. Executing a Cleanup on your working copy will repair these broken timestamps and restore status checks to full speed.

Use Commit Timestamps

Some earlier releases of Subversion were affected by a bug which caused timestamp mismatch when you check out with the Use commit timestamps option checked. Use the Cleanup command to speed up these working copies.