1 computer thinks network has no internet access when it does

I have an ActionTec modem with AT&T service and a LinkSys router. My roommate's computer and my work computer can connect to this wirelessly and have internet, no problem. My personal computer connects to my network, but then says my network has "no internet access" which is obviously false since 2 other computers can use the internet on this network. I've unplugged, turned off, turned on, you name it. Also I know my computer can still connect wirelessly because it works on a public wireless network. Possibly related, upon turning on my computer, a RunDLL error message pops up about how it can't find DisplayOnlineTray. All worked fine with these 3 devices (modem, router, and my computer) until AT&T had service issues last week. When the internet came back, my roommate's computer and my work computer were fine, but my computer can't see the network's connection to the internet. Why is my computer blind to this connection and how can I fix it?