The following simple tabPanel doesn't work in our full sandboxes in FF 3.6.2, Chrome 5, or IE 7.  In my developer sandbox, the code works fine (and I have a much more complex set of tabs).

<apex:page standardController="Account" showHeader="true" tabStyle="account">

<!-- Create Tab panel -->

<apex:tabPanel switchType="server" selectedTab="name1" id="AccountTabPanel">

<apex:tab label="One" name="name1" id="tabOne">content for tab one</apex:tab>

<apex:tab label="Two" name="name2" id="tabTwo">content for tab two</apex:tab>

</apex:tabPanel>

</apex:page>

 
Clicking an inactive tab doesn't work - actually, the error is thrown before click at mouseover.  Here is the error that is reported by IE:

Line: 106
Error: Object doesn't support this property or method

In FF, FireBug reports "element.hasClassName is not a function" on load and on hover, "elementClassName is undefined".

Anybody else having this problem? Once again, both our full sandboxes have this issue, but a developer sandbox works fine.  All 3 sandboxes are on Spring 10.

This seems similar to this post, but is affecting multiple browsers and is a much newer release: 

Thank you.