Single MMS keeps sending

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I sent an MMS to my friend who has the same phone. They are on T-Mobile and I am on O2. About the same time every night they have received the same MMS from me. I checked the report on the original and it said pending. I deleted that message and still they get it. The trouble is I cannot see if its a Desire issue where the message is sent every 24ish hours or its a network issue. The Desire has no out or sent box so I can't check that either. its just that one message. No other since has done the same thing. Any ideas before I ring O2?