Palm Treo 700P Verizon
The "on-board" speaker and mic no longer work at all.
The "native" Palm wired headset with mic works perfectly through the headset jack.
My wired noise cancelling headphones work perfectly through the headset jack and adapter.
I have not tried the bluetooth mode.
This problem killed my use of my Treo 650, and now is affecting my Treo 700P.

On this phone, by design, using the headset jack silences the internal microphone and internal speakers. The situation I am experiencing sounds as if withdrawing the male jack does not result in the device returning to its "default" setting (internal mic and speakers:ON).

Here is an hypothesis for what may be causing the problem (but I don't know how to fix it!):
I sometimes use a 1/4" (female) to 1/8" (male) headset jack adapter to listen to music on my Treo 700P though my noise-cancelling headphones (which have a 1/4" male jack). The native PALM 1/8" male headset jack has 4 contacts (segments), and I assume one contact is for the microphone. The male 1/8" adapter has only 3 contacts (segments), as there is no microphone in the noise cancelling headphones. Could this be the reason the device does not return to its "default" setting (internal mic and speakers: ON)???

Anyone have similar experience and a solution? Soft re-sets, hard resets, cleaning the contacts with alcohol, etc. do not work. I have also tried using and removing the native Palm headset, thinking perhaps the four segment jack would allow the device to re-set to "default". No luck there, either.