When you're tinkering with the design of your Radio Userland weblog, you should occasionally save it as a new theme so you have a backup in case you completely hose the tables or some other element of the design. I save versions of Workbench periodically with the current date in the name because I frequently screw up this site's table-heavy design when tinkering with it. Once you have saved the design, it can easily be restored by choosing it from the themes page.
Last night, I made the mistake of thinking that Radio Userland saves your navigator links as part of a theme. The software will load a theme's default navigator links when you apply it to a weblog, but it won't save existing links when you create a new theme. When I restored my site's theme last night, I expertly wiped out my 50-plus link sidebar.