Wireless Permits Only IE to Connect

Weird problem - I use my new laptop connected to a home wireless network, and IE7 works perfectly. No other internet application can detect the connection - Firefox, Opera, not even ping! System is XP, ISP is AT&T Yahoo (Vista laptop uses the same wireless connection without any problems), no firewall, no proxy. Any ideas on what might be causing this symptom?

 

Although I do not have a complete explanation, here's what fixed the problem. PC was a replacement from the vendor for a defective one - it arrived with McAfee on it, but not enabled. Since we already had a contract with McAfee for the old PC, we needed to find the info to use that contract. Once we located that, McAfee did a complete download, and then everything was okay. What remains missing in this explanation is what was blocking things in the first place - I wasn't using a firewall, and the copy of McAfee on the PC was not activated - nevertheless, it does appear that it had some active hooks. So perhaps uninstalling that version would also have worked (but I'm not going to try that experiment).