I use XP Media Center. I checked the cat5 cable, replaced the cable connector, checked the settings, I tried pretty much everything, except the antivirus…..
I was suspicious when I noticed my LAN was connecting just fine, even moving large files was no problem, but connecting to websites was only good for X seconds; sometimes it would work, sometimes it wouldn’t. Even checking my email was an issue, so the problem wasn’t browser-wise either.
I finally found the answer on a Windows 7 forum. Some users were complaining about having intermittent connection after installing IE8, which was when it first happened to me and the reason I got rid of it in the first place. Another user mentioned a problem with AVG, then another mentioned something about AVG checking up the websites the browsers would visit on the fly, so I deactivated the “Link Scanner” and voilá!
I was so happy to get a steady connection, I don’t really feel like reformatting and reinstalling windows, so if you’re using AVG (free or paid) and you’re not getting a steady connection disable the Link Scanner, restart and see if that solves your problem. If not, you may try uninstalling AVG, or try a different antivirus software.