When I plug in earphones into my HTC Desire S, it dials the phone Every time I plug in my earphones into my HTC Desire S, it  starts calling the last dialed number automatically and starts the music after short interval.  Does anyone know about this problem?
HTC Desire HD Android 2.3.5

I had exactly the same problem, would plug in standard headphones/ earphones/ aux cable to speakers... all of these would register on the phone as earphones with a mic built in for some reason.  it would cut music tracks short and play the next one or start ringing a call. 

strangely, as i was searching for this thread, the problem has self corrected.  All that is different is that I updated ALL of my apps on google app store today.  This is the only factor that I have changed.  Try this!  I hope it works out for you as well as I know how frustrating it was!

best wishes