iPhone will not connect to any wifi

iPhone 3G with iOS 4.1
Never had a problem connecting on our home network or else where.
Now it will not log on regardless where we are.
It shows the wifi networks just won't log on.
Have tried resetting the network settings, reinstalling the iOS, and restoring it.
Have reset our router but to know avail, it just won't work.
Any help would be appreciated.
Thanks,
Mark