Summary of fix from above link (Thanks to Anuj Varma)

1. Install sqllite (32 bit binary for windows) from here

2. sqlite .svn/wc.db “select * from work_queue”

The SELECT should show you your offending folder/file as part of the work queue. What you need to do is delete this item from the work queue.

 3. sqlite .svn/wc.db “delete from work_queue”
 

That’s it. Now, you can run cleanup again – and it should work. Or you can proceed directly to the task you were doing before being prompted to run cleanup (adding a new file etc.)