I ran into a problem in Radio Userland creating categories with colons in their names, such as Workbench: Radio Userland Tips. I have reported the problem in the software's support forum, but in the meantime I appear to have stumbled upon a workaround:
Create the category without a colon in the name (such as Radio Userland Tips), click the category's name on the main Radio Userland editing page, then edit the name to include the colon.
The colon-character bug has been fixed. If you update Radio.root, you won't have this problem anymore.
I posted details in a response to your message on the Radio UserLand discussion group.
Thanks for fixing that.