Some users have reported issues with slow speeds or trouble connecting to Wi-Fi networks with iPhone OS 3.0 and later firmware. iPhone owners who have jailbroken and/or unlocked their iPhones using blackra1n and blacksn0w have also reported problems.
These problems include the inability to connect to Wi-Fi, 3G and/or Edge, lack of push notifications and issues with the YouTube application. Fortunately there are several fixes you can try to correct these data issues on your iPhone:
1. Reset network settings. Touch Settings -> General -> Reset -> Reset Network Settings.
2. Still having problems? Touch Settings -> General -> Reset -> Reset All Settings. Warning: You will loose all of your preferences.
3. For YouTube problems on jailbroken iPhones try installing youtubeFix from Cydia or another package installer.
4. Restore your iPhone as a new phone. This is a slow and tedious process but will reset your iPhone as if it was new from the factory. Although this should fix all of the above issues, you will have to reload your contacts and media onto the iPhone from the computer manually. To restore:
– Connect your iPhone to the computer.
– Run iTunes.
– Under the Summary tab select Restore.
– Select backup if you wish. When restoring as a new iPhone you will not use the backup.
– When the process is complete the iPhone will restart.
– When the Set Up You iPhone screen appears select Set up as a new iPhone.
Of course, after restoring a jailbroken iPhone you will lose the jailbreak and unlock functionality.
iPHONE 5 UPDATE: There are limited circumstances where iPhone 5 users are experiencing slow speeds or intermittent service when connected to Wi-Fi. There are two fixes that might help.
1. Entering manual DNS settings has been reported to help. Navigate to Settings -> Wi-Fi and touch the blue arrow next to your connected Wi-Fi network. Touch DNS and enter Google’s DNS server address (either 22.214.171.124 or 126.96.36.199).
2. Router compatibility issues could mean that WPA2 Personal W-Fi security is causing the problem. Switching to WEP security or removing password security altogether can improve Wi-Fi speeds and connectivity.