my husband and i both had issues with our ip4 working with wifi in our home. it would not connect to our airport extreme. it would connect, however, to every other place we tried.
it turned out that we needed to adjust some settings with the airport...set to wap instead of wap/wap2.
perhaps it is something as simple as that? i say simple, but i know how frustrating it can be. we had our phones for 2 days and did complete resets, etc, and finally i figured it out.