Nmap syn scan problem with Windows 2003 Server

Hi
 
I'm having the following problem.  When I do a tcp
connect portscan to a remote host using the following:


nmap -sT  xxx.xxx.xxx.xxx -P0 -p 80  

.... I get the the right response:
 
Starting nmap V. 3.75 ( www.insecure.org/nmap )
Interesting ports on  (xxx.xxx.xxx.xxx):
Port       State       Service
80/tcp     open        http
 
Port shows open...no problems..so far so good
 


Now when I try to do a syn scan using the following: 

nmap.exe -sS  xxx.xxx.xxx.xxx -P0 -p 80

I get a response saying the port is filtered.
 
Starting nmap V. 3.75 ( www.insecure.org/nmap )
Interesting ports on  (xxx.xxx.xxx.xxx):
Port       State       Service
80/tcp     filtered    http
 


I'm running the same version of nmap on my winxp
workstation and have no problems.  Both the win2003
server and my workstation are behind the same firewall
hitting the same ruleset. Also, the win2003 server has
the lastest updates from MS along with my workstation
including SP2.
 
Any ideas or suggestions would be most appreciated.
 
Thanks in advance
 
Bill Crenshaw



                
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