I had very similar issues with my brand new dell xps 8500 running windows 8 - after searching and searching, trying to find ways to disable wireless and bluetooth completely so I could run with only wired connection, I decided the issue looked suspiciously intermittent like urls were being scanned before being pulled..
I was having issues keeping a connection with a chat room, and random urls, even google searches would occasionally fail. Even though I had unchecked the box for the pre-installed Mcaffee security thing to NOT check urls.. it appears that it was still processing them in some way.
At this moment, I think my suspicion is right, I have now uninstalled the McAfee security suite, and then removed it's "app thing" from the windows start screen.
Now the internet surfing seems fast and without issues after trying dozens of urls, searches etc.
Of course I do not suggest that anyone remove the Mcafee security without immediately installing another anti-virus product such as Kaspersky, or Avaste.
However with my quick testing, it appears that removing the Mcafee has fixed this issue with the constant internet disconnects and random internet fails. I would be interested in knowing if others posting similar issues in this thread are also using the Mcafee.
If I find the problem returns, I will update.