Google has a number of datacenters which may be updated independently of one another. Sometimes your PR may be pulled from a datacenter that has not yet been updated, thus, it displays 0 on the toolbar. Once the datacenters finish updating, then you should consistently see your TBPR in IE and Firefox (assuming you're using the Google plugin for both).
Attention: "role based name" email prefixes such as support, webmaster, info, contact, forum, service, affiliate, admin, traffic, partners, marketing, etc., for our member accounts are not permitted. They are acceptable for a vendor listing, but not for the member email. This is due to bulk email processors scrubbing them for delivery due to extremely high bounce rates. Please apply for membership using a personalized email prefix. Something like email@example.com.
If we discover you signed up with a role based name we will give you only one message to change it. After 3 days your account will be removed if the email is not changed.