One thing I did to fix this problem is you change the sound options(Sonds and ring tones, and Sounds under Phone Options), I changed them saved settings and cange it back to what I had them at originally. It seamed to resest it back to the original Hang up Sound. Not sure if it will works with other but it was a solution for me.
Just go an replacement Tour yesterday, due to trackball issues, although I had complained about the mms bug. I was assured it would not happen on the replacement. First thing I did was send an mms audio file and place a call. Still there, blaring out just after the call. Loaded .419 with hybrid immediately.