Actually it seems xserver-xorg-video-ati 1:6.13.1-1ubuntu3 is at fault.
When i downgraded to 1:6.13.1-1ubuntu2 there is no problem of mutter crashing. but downgrading to 1:6.13.1-1ubuntu3 does not help.
Also to note is that with xserver-xorg-video-ati 1:6.13.1-1ubuntu3 and ...ubuntu4 , if i run mutter with $ CLUTTER_VBLANK=none mutter --replace
then i dont have X crashes.
Actually it seems xserver- xorg-video- ati 1:6.13.1-1ubuntu3 is at fault.
When i downgraded to 1:6.13.1-1ubuntu2 there is no problem of mutter crashing. but downgrading to 1:6.13.1-1ubuntu3 does not help.
Also to note is that with xserver- xorg-video- ati 1:6.13.1-1ubuntu3 and ...ubuntu4 , if i run mutter with $ CLUTTER_VBLANK=none mutter --replace
then i dont have X crashes.