@ try the needle: I wouldn't do it!
I'va used the original earphones, but it also didn't help. For me it seems that the phone changes its profile while (un)plug the headphone. In my situation the phone couldn't change between the internal and external profile and the result was, that the internal earphine, mic and speaker didn't work. Absolutely nothing helped. I gave up and went to bed ......
The next morning nothing has changed. After approximately 12h the phone made some curious noise and everything works now fine. Now I'm happy, but I did nothing. Maybe there a task in WM5 that proofs the internal status and repairs itself?!?! ...or my phone-jack cleaned himself and stopped notifying a plugged headset ;)
Thanks xda-developers and its users for ideas!