this is typical
I've been seeing this frequently too!
try this:
run->cmd /k ping -t $your-dns-address
you can minimize the window and ignore it ALL DAY/NIGHT.
this will keep the path between you and the DNS primed to take/return replies.
The connection is not likely to be oscilating Up/Down, but rather the ISP subnet
you are connected to may be overloaded.
google for PATHPING -- interesting information
edit:
>>and there's never a problem accessing sites through the same setup when we plug the ethernet into a mac
and that's really interesting! :suspiciou