Sure enough, I took a look at the code and there was a problem where some js that should have been in the PanelLists extension was still in the core. When the panel lists were disabled, it caused the bug you were getting. I've moved the code out of the core and into the panellists extension. All is updated in svn.
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If you need me to uncomment or comment out anything for future use, I'd be glad to help in any way.
Thanks for your help!