[Elecraft] K3--Keying suddenly stopped

[Robert Tellefsen]

I was working the 7th District QSO Party, and doing fairly well
at 5w on both cw and ssb.  Then, just after I logged my 103rd QSO,
the keying stopped.

Neither the paddles nor the computer coming through the key jack
will cause a signal to go out in cw mode.  Keying the paddles does
give cw sidetone and the red TX light over the headset jack lights in
time to the keying.  I've cycled through the TEST mode several times,
but to no effect.

Holding the XMIT/TUNE button does cause a carrier at normal power.
Using
either VOX or PTT on ssb generates a normal signal

Either something has suddenly quit on me, or I've accidentally bumped
some adjustment that now inhibits keying.  No smell of leaking magic
smoke, so I expect it is some adjustment that isn't obvious or
documented.
I've dug through the manual and both the MAIN and CONFIG menus, but
nothing obvious.  There is a TX INH menu selection, but it is in OFF
status,
as it was before the keying quit.

I've tried cycling the power, but no change there.  I'm stumped.
Has this happened to anyone else?  Any ideas or suggestions where I
might look for something that is inhibiting cw TX?

Thanks and 73
Bob N6WG