iPhone 2g wifi stopped working

Hi, my iPhone 2g, 16GB has worked fine for years but suddenly I am not able to connect with wifi. I changed the battery and it has been working fine for many months after that. Suddenly it tries to connect to my wireless network and connects successfully. After some seconds it disconnects. I have no broken cables or contacts since I have not opened it after I changed the battery. I also tried to restore several times, also as a new phone. I am running 3.1.3 jailbroken with pwnagetool.

I have tried to reinstall firmware with pwnage tool but the problem persists.