You're router can't get a virus. But if you don't change the default password on your router then someone else can login to it and lock you out of it.
I run OSX 10.4 with Firefox. A week ago, while using the free internet at International House of Pancakes in Conyers GA, I was maliciously redirected to an internet games site while trying to navigate to a wikipedia page. This kind of thing continued until I cleared my cookies, after which I surfed without incident.
I thought it might be an infected router, but I chalked it up to some bad cookies and forgot about it until last night when I met a friend there to discuss some web updates he was working on. [we like to work in coffee shops and iHop stays open after Starbucks closes]
My friend uses Windows XP on an older PC laptop. When I happened to look over his shoulder I saw the same internet games site: candystand dot com. He's a shy guy, so he wasn't complaining about the issue, but I knew he was trying to do this job, not play games, so it all clicked. He too was being hijacked to the same URL. Each time he tried to navigate to any URL he was redirected to an unwanted URL.
I realized the router was causing this issue, so I recommended he clear his cookies. He did, but they immediately reappeared. So I figure this is some kind of an exploit that attacks Windows and Mac alike, but may be more persistent in Windows.
Today my friend is surfing at Starbucks without incident, so the issue seems to be contained in the Conyers GA iHop wifi network. The on-duty manager confirmed that they have had many customer complaints and that they are working to resolve the issue. The poor lady is just trying to keep her restaurant operating smoothly; she doesn't need this kind of distraction in her business.