Web connectivity issues: dns server isn't responding

I’m having trouble connecting to the wireless network at work (no problems at home using the same laptop). From what I read on the Windows site, folks running McAfee have found it to be a McAfee issue. So I’m wondering if Avast (the free version) is blocking my access to the internet on the work wireless network.
The network connection shows that I’m connected to the network, but with no internet access. When I run a diagnostic I get the message “dns server isn’t responding.”
If I run down to the basement and briefly unplug the router, I get a working connection for a brief period (anywhere from 10 minutes to 2 hours). The problem isn’t just that the lost productivity running to the basement several times a day, but the scanning function on our network printer can’t keep up with the connection going in and out so I’m unable to scan documents to my computer.
Does anyone have any suggestions on how to resolve this?

No, how should it do that, the free version has no firewall.