Wifi Troubles

Ok So I've had my 8gb iPhone 3G for just over a year on o2 pay and go, which means that the free 1 year web and wifi bolt on has expired, I've cancelled the continuation of this which would cost me £10 a month but now I'm having wifi troubles at home which I sincerely hope isn't due to me having to pay for my own wifi. Under settings it assures me that I'm connected to my home network but the information bar along the top of the screen alternates between the GPRS indicator and wifi but I can't get web pages to load via wifi even when it says there should be a wifi connection. I've also noticed this connecting screen which I've never seen before has started coming up sometimes when trying to use safari:


Any Help would be greatly appreciated,

Sam

 

left it for a bit and it seems to have got a decent ip address as opposed to the completely random one it had before and has also filled in some other fields. However is there a way for me to manually enter this in future? as it won't let me tap on the field to edit it