1) Best not to use a Pre-n card with a 802.11g router. It usually sort of works fine, but you're not doing yourself any favours.
2) Just out of interest - all the 7230s that I've seen/used have WEP but no WPA - has yours had a firmware upgrade or something?
3) Norton - not specifically related as client firewalls cannot (in theory anyhoo) prevent encrypted signals. Not too good for networking, but never mind.
More thoughts as they develop (takes time....)