Hi Jp
When you have full service on the wifi..can you click on the ">" at the far right..This takes you to a screen which has DHCP,BootP,Static.
Do you have any values for ipaddress,subnet,router and DNS under DHCP?
In my case..my wifi signal is very low(1 bar)..and every time my iphone sleeps I lose the wifi connection and when I "wake" up the iphone after some time it takes several tries before I can get connected..
Here is what i did..I noted down the values for the parameters (ip,subnet etc) and entered them under the STATIC tab..
This seems to alleviate the problem and I can connect every time the iphone "wakes up".
HTH
Gary