I have the same problem with macbook pro early 2008 15,4 inch 2.5 c2d , the thing is from the OSx !! when i boot from 10.6 , it does that ( vertical shadows from the bottom of the screen about 1 inch thick with 1 inch space between them) when i boot from 10.8.5 , works perfectly !!
And i have to mention that i've tried to install the updates for 10.6 , they are downloaded , but the machine NEVER reboots , it stays frozen , so i have to shut it down from the power button !!!