I have Ubuntu 13.04 running on a Macbook Pro 2009, 5,3 edition, one big issue I have with it is the power management, when the ACPI is active, there are some kind of conflicts with the nVidia graphic card driver.
You should try booting without ACPI in order to see if the system is more stable or not. In order to do that, you can edit your GRUB2 when you boot the computer. Press Shift when you boot and you should see the GRUB menu. Select "Advanced options", then "e" in order to edit the GRUB2 file. There's a line in here with parameters like "ro quiet splash". Add to it the parameter "ACPI=off". It means the kernel won't try to handle the power management of your computer. Once you added the line, press F10 in order to boot with the modification.
ACPI=off is not a solution as Ubuntu can't handle power management at all with it, meaning it won't be able to suspend/hibernate neither "see" the battery (but you can still work on battery). I'm fighting with it for few weeks now and didn't find a solution yet.