Thank you very much for the fast answer;
When the freeze happen,i have no error message,with the pointer moving on the desktop,
But no action with mouse clicking;
i shut down by pressing the power off button,at the startup i have to wait some seconds for the disk check;after that the os run normally;
Generally it freeze when i start an internet session...but i dont know if this is the cause...when i restart after the first freeze,the g4 run without problems,but in some days i can have also another freeze after reboot...but always with the pointer moving on the desktop.
I will try to remove the two 256 ram,and leave 1.5 gb.
I forgot to say that i have the same freeze in osx 10.5.8,with no mouse.now i have removed that hd because i dont need it.