Back before people got MMS working on Virgin Mobile phones that's what happened if you got an MMS. So uh, double check that your ROMs have working MMS. I think all of the current CM7 one(s) should, but I don't know about the CM9/ICS one.
hmmm if you say it could be an mms i bet thats what it was, my friends send shots of their homework when they need help and i was helping a friend when it happened. Il try t replicate and report.