Those users who rushed to jailbreak iPhone 4 with early release of JailbreakMe 2.0 reported some MMS and Facetime issues. These problems now have been fixed and all fresh jailbreaks will be free of such problems. However, the existing users can use one of these methods to resolve the issues on their iPhone 4.
Method 1 to Fix Facetime and MMS issues:
In this method you will need to upgrade the Cydia completely followed by a reset of network settings.
Step 1: Wake up the Cydia and let the loading to finish it.
Step 2: It will ask you to update the Cydia. Press “Complete Upgrade”.
Step 3: Reboot your iPhone 4.
Step 4: Now go to Settings –> General –> Reset –> Reset Network Settings.
Step 5: Reboot the iPhone 4 again.
Method 2 to Fix Facetime and MMS issues:
If the method 1 fails and you still face the same issues, apply this method in which you restore your iPhone to iOS 4.0.1 and rejailbreak it with JailbreakMe tool.
step 1: Download the latest iTunes 9.2.1.
Step 2: Download the iOS 4.0.1 for your iPhone 4.
Step 3: Launch iTunes and select your idevice from the devices list.
Step 4: Now click Shift+Restore (on WIndows) & Option+Restore (on Mac) to start the restore process.
step 5: Browse to iOS 4.0.1 and restore it on your iPhone 4.
Step 6: After the restore is completed, follow our iPhone 4 Jailbreak Step by Step Guide to re-jailbreak with JailbreakMe 2.0.