WIFI problem on home network with i phone 4 iPhone

Hey can someone please help me, my iphone 4 is connected to my home network and it is unable to connect to safari or the app store as it says that the device is not connected to the internet, but when you go and have a look at the settings between the network and my phone it usually hasnt found any of the details about our home network, and on some occasions it finds only the IP address and the Subnet mask. Once again i will say that this problem only occurs on my home network and not at any other network.
Another problem i have is that my 3g simply doesnt work the symbol is there and all and says it is working but it does not.
Windows 7