Browsers And Pidgin Died When Installed Router

It all started about a week ago when i upgraded at home from cable modem + router to a Cisco combo provided by the ISP - Cisco EPC2425. We have 5 PC's running locally - 2 physical and 3 wireless, and out of them my PC is the one with the problem, the rest are just fine - i'm typing this from one of the laptops.I run XP Pro SP2 Version 2002. The PC is a E6300 with 2x2GB of DDR2 800 ram, motherboard is Gigabyte EP31-DS3L, and video is a Leadtek 8600GT.I use the same software for close to 2yrs now - only difference is the AV which has been Kaspersky 2010 for 3months.I use the XP firewall.As browsers i use the latest Firefox with NoScript and the latest Opera.The problem was that soon after we put in the new combo my browsers died. Pidgin has issues, Opera actually manages to check a page.I have tried repairing the connection, uninstalling the connection, uninstalling the LAN, disabling noscript, changing my DNS - it is taken automatically from the router and the router has DHCP and i'm not really sure that i managed to change it either, and even reinstalling the OS. Reinstalling the OS seemed to fix the problem, i did not have it for almost 5 days, but all of the sudden, it's back, and it wasn't simply in full effect, it was gradual. It started as pages taking longer to load, having to refresh constantly to get them to work and after a restart, they stopped working altogether, yet Opera is still working - not sure for how long though.MMO's work, WoW and EVE have no issues on the affected PC.I'll try to be a bit more clear. Router was installed, my browsers died, everything that would require a DNS died, and so did pidgin - i use google and MSN on it. I reinstalled the OS, and it worked fine for 5 days, than it started again. Current status is MSN not functioning, Firefox not functioning, Google talk functioning 50% of times, and Opera still functioning - not sure for how long.PS: No, i did not have norton installed.