Anyone at Verizon who is paying attention would realize this problems is many years old with no solution. People are literally begging for help in dozens of online forums, to no avail (Google search usually provides me results faster than any tech support). I have the exact same issue. All my wireless devices connect to the internet through the Verizon MI424WR router with no problem. My Vista laptop connects just fine via Ethernet cable, but not the wireless. I can make a wireless connection to the router, and the router admin page shows it is, in fact, connected, but absolutely NO connection to internet is possible.
BTW, the laptop had no problem for years connecting to the internet via a Linksys WRT54G connected to Verizon DSL.
All that the troubleshooting "guide" provides is the usual basic "plug in, turn off, turn on, reset" nonsense that might help only those who can't stop their VCR clock from blinking.
So please, Verizon, bump this up to a FAQ (because it is VERY frequently asked), and help us find a solution.