Cisco 851 port 80 TCP forward does not work

I am trying to map all incoming Internet port 80 traffic to an internal web server. I have successfully done this with several other services like FTP, SMTP and POP3. See my running config below:

ip nat inside source list 1 interface FastEthernet4 overload ip nat inside source static tcp 192.168.1.101 17307 interface FastEthernet4 17307 ip nat inside source static tcp 192.168.1.101 6881 interface FastEthernet4 6881 ip nat inside source static tcp 192.168.1.132 993 interface FastEthernet4 993 ip nat inside source static tcp 192.168.1.128 6100 interface FastEthernet4 6100 ip nat inside source static tcp 192.168.1.128 25 interface FastEthernet4 25 ip nat inside source static tcp 192.168.1.132 990 interface FastEthernet4 990 ip nat inside source static tcp 192.168.1.132 5000 interface FastEthernet4 5000 ip nat inside source static tcp 192.168.1.132 110 interface FastEthernet4 110 ip nat inside source static tcp 192.168.1.125 21 interface FastEthernet4 21 ip nat inside source static tcp 192.168.1.115 80 interface FastEthernet4 80

The port 80 mapping does not work. All HTTP traffic from the Internet is redirected to the Cisco SDM login page. If I disable SDM, I get page cannot be displayed. I've searched everywhere for an answer but haven't been able to find anything.

Any help is appreciated!

--Paul