I recently upgraded to 4.0.1 JB using JailBreakMe. I've heard that ultrasn0w could cause the problem, but I did not have it installed when the MMS problem existed. I tried with ultrasn0w installed, installed ultrasn0w, reset network settings, all with reboots in between. I can't seem to figure out why this is happening. Anyone have any ideas? I tried the fix: http://forums.macrumors.com/showpost.php?p=10812249&postcount=6 and it still doesn't work. Thanks in advance.