Strange FC3 internet problem

[Catalin Leanca]

I'm using Fedora Core 3 with all released updates.
My computer is LAN connected (routable addresses)
An Cisco 3550 Multilayer switch is the internet gateway for this LAN.
After boot i can't access any location outside my LAN on any port except ICMP packets.
For example "ping www.google.com" works perfect and "telnet www.google.com 80" no response.
telnet on port 80 on my LAN web server works, as well as all others services in my LAN.
Linux Firewall is disabled, SELinux is disabled, ipv6 disabled too
On Cisco 3550 no ACL is present.
After a number of unsucceded tries in firefox browser (to google or other outside site) everything 
starts to work normally,
i am able to connect to internet on any port.
After reboot the problem is still there.


Thanks, Catalin L