Pale Moon forum

I'm using Vimperator and for some reason it gives me this error-message with a fancy red background:

TypeError: tabGroup.tabView is null

What does it mean and how can I solve the problem?

Pale Moon does not ship with the tab group. The Add-on for some reason expects it. You can solve the problem by installing the Pale Moon Tab Groups add-on from here: http://www.palemoon.org/tabgroups.shtml

Thank you!