The one thing I've heard (with mixed results) was to reset your network settings. In the Settings app, General, Reset, Reset Network Settings. This will erase any saved networks (you'll need the WEP/WPA keys and/or settings to re-add), but hopefully that's all you'll lose. I think there was another thing to try with an app in Cydia, but hopefully someone more knowledgeable about that will chime in soon.
05-10-2010 12:43 PM