"This has resolved many issues and worth a try.
- Sometimes after you perform a upgrade from say iOS 3. to iOS 4.2 *the iPad or iPhone wifi or 3G speeds *may be slow.*
- This is an easy fix which does work. Please do the following:
1. Go to Settings->General->Reset
2. Then select "Reset Network Settings" (this will not erase ur devices content, music, videos, email, etc. It will only erase any WiFi networks you have defined).
3. Once your device completes the action and gives you the normal home screen or Passcode screen, go ahead and power your device down and once you are sure the device is fully powered down wait an additional 60sec to allow internal components to fully discharge.
4. After the 60sec is up, power on your device again and re-add any encrypted WiFi networks you had defined.
5. Enjoy the "back to normal" WiFi and 3G speeds like you had prior to the OS upgrade.*
col.bris, Brisbane Australia
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Hope this helps