my iphone disconnect from wifi all the time. every time i start to download an application from installer or cydia i get errors: host not found or source.....etc
i hv problems with fring, it goes down everytime.
to get wifi working i must restart iphone

Try a different Hot Spot. Also, check your router & firewall settings. It doesn't looks like an iPhone's fault to me. And if nothing works, try a DFU restore. Good luck

Yea I would also double check the HotSpot. If nothing works, you have a warranty :iphone: