I have the newest AirPort Extreme that transmits simultaneously in 2.4GHz and 5GHz. It's been great. My speeds have jumped 2-3x what they were before I upgraded to this router. Now, I'm getting 28-30MB per second download speeds. Before this I was getting 8-10MB per second. But, I have a problem. My MBP connects great to the AirPort Extreme (802.11n at 2.4GHz or 5GHz). One PC desktop works great with the AirPort Extreme (via Ethernet). And, I have another PC laptop connecting at good speeds (802.11g). But, I have one other PC that sees and connects to the Airport Extreme signal (802.11g) but nothing happens. It's like a garden hose with very little to no water. The signal strength is very strong and, again, the computer DOES recognize the signal. It's an XP desktop (4 or 5 years old) with an 802.11g card inside. Any thoughts as to why I have this problem with this one computer? It connected fine with my prior wireless router. It's a new problem. By the way, the Airport Extreme is setup with all of the normal defaults and "automatic" settings, WPA2, etc. My cable provider is Comcast and the router gets it signal from a new modem. There are no other routers, etc. Thanks for any ideas. I've researched this for hours (and have called Apple). No answers so far.