FirePHP 0.3 introduces a feature that will only add the "FirePHP/" string to the user-agent header if "Firefox/" is found. This change is incorrect and will be reversed in 0.3.1. The FirePHP string should be added to any existing user-agent string as long as FirePHP is enabled.
Workaround: Install
User Agent Switcher and edit the user agent string to include "Firefox/...".
For more info see:
Issue 110FIX: Upgrade to 0.3.1 here:
http://www.firephp.org/HQ/FinalRelease.htm