I recently had to debug a JavaScript error in the MCMS console that would occur when the user would switch to edit mode on the homepage template, and not any other template.

After some testing of the CMS JavaScripts I determined that the error was occuring in Console.js, UpdateSiblingFramesInUnpublishedMode().

A quick search of the web found: http://download.microsoft.com/download/4/2/5/4250f79a-c3a1-4003-9272-2404e92bb76a/MCMS+2002+-+Web+Author+FAQ.htm#A0F55902-5FC0-4A0E-A449-C8318564077F

As the item indicated, the site's only template contained an IFRAME, which was exposing the MCMS bug.  I updated the code as indicated, and the problem was resolved.