I really don't yet quite understand what is happening to the MMS and Yahoo Messenger. That they just don't work doesn't really tell me what is occuring. Is the Yahoo application deleted? Does the MMS function on the Message menu go away, or just not sent and you get a red X by the message, or are you not receiving?

The MMS function of the BB requires a Service Book (options, advanced, service book). Perahps that is getting deleted somehow, but unlikely unless you are doing so.