Meeting with 12 attendees is crashing

a client is running a meeting with 12 attendees and it is crashing.

they are using áudio and vídeo for the meeting.

accordingspecifications, all clients are using propper machines. what is going wrong?

thanks in advance for any help.

here are the specifications of participants:

Group A

10 unid - Notebook HP 240 [ Intel Core i3-3110M graphics Intel HD 4000 ( 2.4GHz, cache 3 MB, 2 nucleos ) DDR3L 4GB 1600 MHz ];

10 - Windows 7 PRO 64bits;

6 - Link 10 MB ;

1 - Link de 17 MB ;

1 - Link de 5 MB ;

1 - Link de 15 MB ;

1 - Link de 4 MB ;

6 - Browser Google Chrome;

4 - Browser Internet Explorer;

GroupB

1 unid - Notebook Lenovo G470 [ Intel Core i3-2310 ( 2.1 GHz, 3MB cache ) PC3-10600 DDR3 4 GB ];

1 - Windows 7 PRO 64bits;

1 - Link 4G -  2MB ;

1 - Browser Google Chrome;

GroupC

1 unid - Notebook HP 450 [ Intel Core i3-2370M  graphics Intel HD 3000 ( 2.4 GHz, cache 3 MB ) DDR3 1600 MHz 4GB ];

1 - Windows 7 PRO 64bits;

1 - Browser Google Chrome;

1 - Link, 4 MB;