We are sorry for the inconvenience. We have found and fixed the problem so you should be able to remove the folder you wanted to remove.
The worksheets that are on the recycle bin will be automatically removed, so you don't have to worry. But as you saw you can empty the recycle bin if you want. That won't give you any more problems with the folders.
We hope this solves the problem you had, if this is not the case or additional questions or doubts arise, please let us know.