Early users of JailbreakMe.com may have experienced problems with MMS and FaceTime.
First of all, as of right know JailbreakMe.com have fixed the problem so new users will not experience that problem.
For existing folks with the problem, re-jailbreak will not fix the issue.
The fix itself is very simple from twitter via planetbeing:
chmod 755 /private/var/mobile/Library; chmod 755 /private/var/mobile/Library/Preference after that Reset Network Settings
Also, as of right now cydia is updated, update cydia and that should fix the issue – via planetbeing