The same when connected to any other wi-fi network besides your own?
Did you transfer the backup for your 3G to your iPhone 4?
If so, try resetting network settings on your iPhone 4 at Settings > General > Reset > Reset Network Settings.
This will require re-joining every wi-fi network your iPhone 4 has access to when returning within range of such a network.
Does your wireless router support WPA encryption? If so, change it from WEP which is very old and not very secure. You want to use WPA especially if you have any Winoze computers or devices connected to your wireless network. WEP can be easily compromised.
yes i transferred the back up from my 3g - which has no problems at all staying connected to the wifi.
I have tried resettng everything and have lost count of the number of times I have had to reenter the wifi pass word.
The router settings are set to WPA-PSK with TKIP encryption (what ever that means!) and the easy pairing tick box is checked
The backed up data in this regard for your 3G has nothing whatsoever to do with your 3G not having the same problem. Some of the data in the backup may be corrupt, etc.
What does you have tried resetting everything include?
Does this include resetting network settings on your iPhone 4 and/or include restoring your iPhone 4 as a new iPhone or not from the backup?
Do you connect your iPhone 4 to any other wi-fi network besides your own? If so, does the same occur with every wi-fi network you connect your iPhone 4 with?
In your original post, you said WEP password.
Have you checked the manufacturer's website for your wireless router to see if a firmware update is available for your wireless router model that you haven't installed?
yes have reset the network settings - just did it again after reading your reply
sorry if confused you by saying WEP password - what I meant was the password that is on the back of the router and has to be entered before you can connect.
The router is new and was replaced just a couple of weeks ago. I have also totally disconnected it and rebooted it a number of times in the hope of curing the connection problem.
I have only had the Iphone for a week so I have not been anywhere to connect to anyone else's network apart from using 3g or btopenzone when out and about.
The only thing i have not tried is restoring the phone as a new iphone on itunes
hope this helps