Pidgin 2.10.9 - Media Buttons greyed out on XMPP

[cos667]

Hi,

I am using Linux Mint 16 and Pidgin 2.10.9 (from developer PPAs).

I can connect to Google and chat but Media Buttons are greyed out and I 
can not start
any voice/video calls.

Details:
- several Pidgin versions tested before this including 2.10.7
- several connectivity options tested (XMPP>Advanced)
- Google talk plugin installed (Firefox hangouts with video/voice are 
working)
- gstreamer0.10-plugins-ugly and gstreamer0.10-ffmpeg are installed
- notification sound are working

Many thanks for your support.

Cosmin