here you go
http://blogs.zdnet.com/Bott/?p=10
"The culprit is the built-in firewall software on the DI-724U router, which features Stateful Packet Inspection (SPI). This is not the only router in the SOHO market that features SPI - Netgear's WGR614 and Linksys' WRT54GS are among dozens of products that offer similar capabilities. Trouble is, the new and improved TCP/IP stack in Windows Vista falls apart when it encounters an SPI-enabled router.
One workaround is to disable SPI on the router. That significantly weakens a key layer of network security, but it allows Internet traffic to get through. Unfortunately, the D-Link DI-724U, like several other products in the same family, doesn't allow SPI to be disabled"
