Microphone not picking any sound -- Debian Testing/Wheezy (KDE 4.6.5)

[Arun Khan <knura9@gmail.com>]

Debian Wheezy AMD 64 weekly build 13/Feb/2012
KDE 4.6.5 (default) desktop
Kernel 3.2.0 (stock from the weekly build)
on Toshiba C640 laptop.

alsamixergui shows - audio device is shown as Intel Conexant CX20590.
I can hear sound from the built in speakers as well as from the head phone jack.
Through Kmix gui, I have boosted the Mic to 40dB.

However, the mic does not pick up anything.  I am unable to use
services like linphone and skype.

FWIW, in KDE>System Settings>Sound and Video Configurations> Device
Preference> Audio Capture
Communications shows the "test" button greyed out whereas the same
system when I boot with Linux Mint 12 KDE RC (Live Session), the
button is not greyed out.

Any pointers to get the MIC input working highly appreciated.
-- 
Arun Khan