Earlier today, Apple has released iOS 5 beta 4 to developers for iPhone, iPod touch, iPad and Apple Tv. As we reported you that Apple has introduced OTA (Over-the-Air) feature which allows you to download iOS update directly to your iOS device without using iTunes. Unfortunately jailbroken device can't use OTA feature.
Source- HEREToday MuscleNerd of iPhone dev-team has confirmed that OTA update won't work on jailbroken devices due to an explicit check of Applications. MuscleNerd didn't give any other details, but I think this is a new challenge for iPhone dev-team.
Guess jailbreakers will have to restore to iOS5 Beta 4 then jailbreak. Although, I'm skipping beta 4. I was on Beta 3 and went back to 4.1