This might help out with why the X server crashes when you are either running a video, multitasking, running a video while multitasking or simply have too much eye candy.
Basically there is more memory being allocated to the PS3 frame buffer which is not giving enough memory to the other programs when you have to much things going on thus making them having to go on swap.
A way of overriding the default frame buffer default settings is to insert ps3fb into the append line of the yaboot.conf file.
So here is a regular append line in my yaboot.conf file:
NOTE: The number that is equal to ps3fb is different for each one because it takes more memory to display linux at a higher resolution. Just use the numbers I chose for a precaution. But DO NOT copy and paste what I have above, because I did not accept the system defaults for the partition table on the Other OS side of the PS3 and it could mess up your install. For some reason not accepting the defaults changes the yaboot file in some way. So just insert ps3fb=#.
Save and reboot. You should now have a hard time crashing your X server instead of having it crash on you!