Telephony function suddenly failed

When I call another phone(land line or cell) from this HTC, it rings and connects but there is no sound on both phones.
If I call from another phone I immediately get the voice mail message bank telling me to leave a message. My phone never rings or vibrates.

This just suddenly happened. The phone was not dropped.
The speaker works fine, but the speaker phone symbol is greyed out when I am connected.
I have verified the correct function of my SIM in another cell phone and I have tried resets and battery removal. The HTC works well with all other functions, GPS, Wifi, games, etc.
I have not installed any new software in the past 6 months.

I would also appreciate hints where to look if this is a hardware issue.

[studentjunk]

my speaker phone icon greys out when i have a bluetooth headset connected. I would take it in to the service provider and ask them for help.

Have you done a hard reset? It sounds like a software problem, and not a hardware problem (not that i know for sure).

[thej0ker]

That's odd. Mine just did the exact same thing. I figured the phone had just failed. I filed insurance claim on mine and got a RAPH500 instead of a RAPH800, kinda pissed me off!

Yes I tried resets including hard reset.
I ripped the bugger apart to all it's bits, washed out the connectors, was astonished that it ever worked at all when I saw how flimsy it is all held together, got it all back together again but nothing changed.
It is now a PDA with GPS for the kids to play with.