I have JB about 15 i4s over this last week and about half turned out ok. I have been JBing phones since os2 (well over 100 phone/pods) and this is by far the worst JB I have ever experienced. Aside from the wifi and mms problems, four of the phones have a problem were videos won't play and the ringer has no sound when a call comes in. If you reboot they both work for a few mins then go right back to not working again. I have even tried restoring and just JBing and not installing anything from cydia but still get the same result. Anyone else experiencing this?
It might help to tell us what OS you're on and what jailbreak you're using. There are now 2 jailbreaks for win and OSX. Never restore from
A backup in iTunes also.. Always set up as new when having issues.