Do you have a cable/adsl modem and also a 56K modem?
I get the same irritating popup when i try to visit some sites (not even porn).
I have a cable modem, and also a 56K modem.
But still those sites want me to use the Dial-up connection, but when i klick cancel, i get a 401 error.
So, it looks like they are sending some sort of a Dial-up request, even when you are already connected through a cable modem.
So, for me the only way to visit those site's is to use my Dial-up connection.
It could be a bug, i don't know!
But it's nice to know that i'm not alone.
It seems you have some little program that is running when you start windows, and whatever it does it needs to access that ip address. Go to task manager (ctrl+alt+del) to find a process that looks funny, then search for it in your C: drive and delete it, and then go into your registry and get rid of it.
If you don't see anything that jumps out at you, be sure to get adaware and the latest ref file and give your computer a full scan, it kinda looks like it might be spyware that was installed with something, and adaware will help you find it. Last, do a full virus scan (be sure to update virus files first), it might even be a trojan that is trying to send information somewhere.