This is for those who's auxillary or output would allow you to hear your call but your caller was unable to hear you.

I finally gave in and contacted WebOS support and spent 15 minus talking to tech support tonight and he had me hold the power button in, and toggle the mute switch 3 or 4 times, it did a funky reset, I plugged in a set of head phones and it works properly.
Prior I had tried WebOS Doc and various updates, I even had the problem with a replacement Pre. It seems that the device was stuck under some other application while accessing the mic.

Try this, let me know if it works for you, and as always, us the "thanks" button!

Also, will send the tech log for anyone having further issues.

I've posted this in every thread I could find regarding this issue.