It will freeze at random times usually during gameplay. Not in the menu or when loading.
Could you enter 'trace(1);' into the commandline and post your console.log?
I am not sure, but from what I read
here on the Blockland site. You need a graphics card compatible with Open GL.
Your Radeon X300,
as read here, may not support that with the current drivers.
So maybe updating your driver may solve your problem.
I couldn't find the drivers on
the AMD site, maybe you have more luck.
Otherwise, try one of the drivers
from here that is compatible with Win XP.