Using the WebBrowser control in VB6

I have developped an application in VB6 where I have to use the WebBrowser control. My development environment is Win2K professional, my default Browser is Mozilla Firefox. Everything works fine under Win2K. When I install my application in another machine running under Win XP, my application works fine, and display a web page in my WebBrowser control, but some buttons with hyperlink do not work. It does not take the user to another page. The next page is under a secured section of the web site (and yet it works under Win 2K). I have reset all the internet options to the default settings ( for IE and Firefox). Does any one has any idea on this problem ? Please help (the release date is coming real fast)