But don't worry: it is easy to fix in a few steps:
- Create a copy of the affected folder and move it to somewhere outside your working copy.
- Clear the copied folder of all SVN-references (e.g by deleting all .svn folders).
- SVN-delete the affected folder (either be SVN CLI or from the context-menu when using tools like Tortoise/Rabbit-SVN) - if the folder contains subfolders make sure to also SVN-delete these as the SVN-delete command is not recursive.
- Commit the deleted (and only the deleted!) folder.
- Delete the folder from the filesystem.
- Copy the aforementioned copied folder back into the working copy.
- SVN-add the folder.