Javascript, innerHTML error in Firefox

[roblawrenc]

I have a list generated by a database pull for a contact list. When you
click on the name, I want the iframe to the right to load another page
to view the contact information (using innerHTML to accomplish this).
This works on the first click, but then when I click another user name,
I get the following error in Firefox Javascript console

Error: top.mainFrame.rightframe.document has no properties
Source File: http://www.biggerstring.com/email/addressbook/frames.php
Line: 226

Here is the line it directs me to
temp = top.mainFrame.rightframe.document.title;

Everytime i change the iframe on the right, i had it named rightframe
with the same id.

This all works in IE though. Any suggestions are appreciated. Thanks in
advance.