Phone sends text each time messaging is opened

[Guest nickw]

My Wondows Mobile 6.1 (on HTC TyTNII) seems to have developed a fault whereby each time I open up messaging it then automatically sends a previously sent text to one of my friends, she thinks she received about 50 of the same message. I've rebooted but no change, so I've now deleted all messages in my inbox and outbox and will see if that fixes it. Anyone else had similar problems?