Right click on your Subversion working directory folder, and select TortoiseSVN->Clean Up from the Context Menu. This will recurse it’s way through your working directory and cleanup any incomplete actions, remove the local locks (which is different from using Subversion locking of a file in the repository which lets everyone know about the lock).
If that doesn’t work, see if you can find the names of the files that were changed, but not yet committed, save them, and redo the checkout.