For anyone else having this problem, note that it is an issue with doubleclick ads. They use a variable called openWindow which of course conflicts with the function name.
Adding this condtional to your ads in the template should fix it:
Code:
<if condition="THIS_SCRIPT != 'editpost' AND THIS_SCRIPT != 'newthread' AND THIS_SCRIPT != 'newreply'">
AD CODE GOES HERE
</if>
We have notified Google and doubleclick in hopes they will change the variable name.