It could be spyware, but that usually wouldn't affect anything but IE like this. Still, can't hurt to check.
There's also every chance that since it happens in every browser, that it's a problem with your ISP's DNS system. Call up their tech support and make sure you have all the settings correct and see if you can't convince them to get someone to look over their DNS server configs.
Using XP Professional and any browser. (IE or NetScape 7.1 or Mozilla), there are numerous sites, popular sites, (Yahoo-Microsoft-Download.com-CNET-Ebay-Comcast, etc.) that I cannot reach by entering just the URL. Some of them, I can reach by clicking a specific link, that does not have the stock www. address contained in the link, such CGI.Ebay.yada. This happens in all browsers with the timeout message in Netscape and the Unable to open page in IE. I'ev tried everything short of wiping my drive clean and reinstalling everything, and really don't want to do that. Any suggestions?