|I figure you probably won't believe this but I had the same problem.|
It turned out to be the HP Print from internet program. Kept logging itself on to the net and then disconnecting the computer. Then the computer would reestablish the connection.
Took me almost a month to find the damn thing.
Uninstalled that one part of the HP 's MANY programs it loads when it installs and the problem went away.
Very, very weird, but it worked.
What I hear, I forget. What I see, I remember. What I do, I understand.