Apache with IIS on W2K - configuration problem

I am developing a web site (PHP/MySQL based) for a client who has recently installed Apache (2.0) along with PHP, MySQL, etc. (Apache2triad package) on the same W2K box where they are also running IIS (different IP). When they first installed and configured it, it worked just fine. I was able to FTP files and could view pages that confirmed that PHP and MySQL were working OK. But after a couple of days, every attempt to view pages results in "The page cannot be displayed" message. (Pages still display fine on local machine, though.) Surprisingly, I am still able to FTP files to the server (using domain name, not IP). My guess is the problem is related to some firewall settings that my client probably made. Although they say the settings are good and all needed access is granted (HTTP, HTTPS, SMTP, etc.).

Now with this limited information, can anyone suggest what might have gone wrong and why my FTP software can access the Apache server but pages don't display in browser? If any more info is needed, please let me know and I'll try to get it.

Thanks a million.

Really hard to tell, but it def sounds like a firewall problem. Many desktop firewall apps (assuming they're using one) aren't the best at dealing with multiple IP's... the settings they've entered are probably fine for the primary IP, but not the other (i.e. what ever Apache is running off)