Mozill firefox browser is not getting recognized though the required plug-ins(Firefox Support, Web Testing) are available & enabled in the test complete "extension" dialog.
As for Google Chrome and Apple Safari, these browsers are not supported. We have suggestions to implement this functionality, and your request has increased their rating.
BTW, support for Firefox 3.6 will be included in the next major version of the product - TestComplete 8. It will be released in a month or so.