Ever since JailbreakMe Star tool was announced by the iPhone dev team today, lot of people are busy jailbreaking their iPhones and iPod Touches. We have also posted guides to Jailbreak iPhone iOS 4.0.1 and iPod Touch iOS 4.0.1, but then iPhone 4 users reported that Facetime and MMS applications stopped working since jailbreaking their device using JailbreakMe 2.0
Well, there is a fix released for this issue and users can follow this simple guide given below, courtesy BlogsDNA
[How to] Fix FaceTime & MMS Issue on iPhone 4 After JailbreakMe
1. Restore your iPhone 4 to iOS 4.0.1 with iTunes 9.2.1
2. Downlaod iOS 4.0.1 for iPhone 4
3. Connect your iPhone 4 to PC/Mac
4. Start iTunes and click on your iPhone from the devices list
5. Now click Shift+Restore (on Windows) & Option+Restore (on Mac)
7. Now browse and select iOS 4.0.1 downloaded in step 2.
8. Once you have completed restore process, follow our guide iPhone 4 Jailbreak & re-jailbreak with JailbreakMe.
The key is to restore back to iOS 4.0.1 and re-jailbreak with JailbreakMe to fix Facetime & MMS Issue.

Raju PP is the founder-editor of Technically Personal, which is one of the most widely read technology blogs on the web. He holds an Engineering degree in Electronics & Communication, and has previously worked as a Technical Specialist in Banking Software domain.
what about normal restore, without Shift+Restore