Vista - Intermittant internet/Outlook connection problems

Ever since I started running Vista Home Premium, I've had intermittant
internet and Outlook connection problems. Two or three times a day, the
connection just hangs up. If I try, and retry, and retry, I usually get
through. If not, I always can get through by closing and reopening IE or
Outlook. I know this isn't a Verizon DSL problem, because my wife's machine,
running XP, is connected to the same modem and never has problems. We're
both hard-wired to the modem, so it's not a wireless problem. On the IE
side, it often seems the hangup is when the machine is trying to load some
advertisement, on the Yahoo site for example. I've also tried to explore if
this is a firewall problem -- I'm running Norton 2007 -- but I've made all
the changes they've suggested, with no ultimate effect. I also don't think
it's an IE 7 problem, because the same problems occur when I run Firefox.

Any ideas would be most appreciated.
--
SFB