MY MAC HARDWARE TEST ERROR :4MEM/9/40000000 : 0 x 82138790

Hi,

My MacPro has detected 4MEM/9/40000000 : 0 x 82138790 and recently has restarted itself while I am working on the computer. I am a stock trader and I need to open 5-6 windows at once so i consider as a medium-heavy user. They are all web-based trading platforms and I don't download stuffs into this computer.

Here is my MacPro info

14 months old

OS X Version 10.8.5

Processor 2.3 GHz Intel Core i7

Memory 4GB 1600 MHz DDR3

My questions are 1) how to fix this problem? 2) what and how should I increase my MacPro's capacity and ensure the same problem will not happen again?

Many thanks.