Windows 7: Limited or no connectivity with a wireless connection.

Hi there i am going crazy here. I upgraded to XP Home SP3 from SP2. I have a Belkin Wireless Router N and a Notebook computer with a DLink Adapter G. Previously i had no connection problems. Now since upgraading if i leave my Wireless connection OPEN or with no password it connects no problems at all.When i try to put secuirty on the connection it comes up with the "Limited or no connectivity" error. I have tried everthing that i know. Any ideas out there? I cannot leave my wireless connection without a password. Thanx,, Kakadu