So my friend has this dilemma, he used to go on this one forum website {FF merch site} and he can get in fine every time, but just about a week almost two ago he can't get on without using a proxy. I tried googling but I kept getting generic answers and we tried unplugging the router/resetting/leaving in alone for a few hours. It'd be nice if someone can help :/ {He wasn't IP banned cuz this other forum did it to him too}
It might not be a specific IP ban but a range of IP ban using wildcards such as 102.*.*.* meaning no matter how many times the IP is reset through restarting of routers etc, since the ISP usually changes the last few wildcards specifically the last two for IPv4, there wouldn't be any help. Otherwise it might be that the ISP has blocked access to it or the router is blocking the connection. Try doing a run>cmd>ping URL to see there's any response at all. If yes, then do a run>cmd>tracert URL to see where the connection is terminated. It could also be that the DNS isn't updated, try doing run>cmd>ipconfig /flushdns as well.
Get them to try Hotspot Shield/Tor http://www.torproject.org/ http://www.hotspotshield.com/ Although Tor apparently has some unfavourable things in the bundle when you install it. :$ So try HSS first
The Tor Bundle also installs Pidgin Portable and other stuff most people never use; just delete the program files for those. (And error pops up saying "Unable to start configured IM client." or the suchlike, but Tor still works fine. n.n
I had this very problem today, fixed it in 5 seconds. Just do a ipconfig /release then ipconfig /renew