Thomson Speedtouch 510 and Windows XP Pro SP2

I am using a Thomson (Alcatel) Speedtouch 510 (adsl modem/router) and Windows Xp Pro SP2. I have 3 PCs connected to this router via DHCP. Since I installed SP2 on my main PC, I can no longer connect to the router to check/configure it, even when I turn off Windows Firewall. I use IE6 (uPnP) to connect to the router.

When I uninstalled SP2, everything is back to normal. Only with SP2 installed that I get the problem of not "seein" or "connecting" to the router.

There is no problem with internet connection at all. I can email, browse, etc. I just can't talk to the router to re-configure or check its status.

I am almost quite sure the security settings of Windows XP Pro SP2 is creating the problem. Right now I had uninstalled SP2, but would like to install it if I resolve the router "see and talk" problem.

Is anyone familiar with this router?

Please help, and thank you in advance.