To fix your MMS and FaceTime issue, simply follow these steps:
- Go to Cydia and add this source: http://iphonedelivery.advinux.com/cydia/
- Once this source has been added, install “iPhoneDelivery” from it.
- Reboot your iPhone
- Go to Settings > Phone > Turn FaceTime ON
If you use JailbreakMe now, you shouldn’t have any problem as it’s been updated to fix the issue. If you can’t wait for the official fix and if you don’t want to try this unofficial fix, you can always restore, and jailbreak again with the updated JailbreakMe.