Horizontal and vertical coloured lines on MBPro. Why does this occur?

1. Reset SMC. http://support.apple.com/kb/HT3964

Choose the method for:

"Resetting SMC on portables with a battery you should not remove on your own"

2.Reset PRAM. http://support.apple.com/kb/PH4405

If this does not help, contact Apple.

Best.

Which model MacBook Pro do you have (e.g., "15-inch Late 2011")? The 15" 2010 and early and late 2011's have some problems with the GPU...

Clinton

Mid-2010 15" MacBook Pros - the bad NVIDIA GPU

If you're having frequent kernel panics with your 15" mid-2010, or intermittent screen problems, the problem is, more than likely, the faulty NVIDIA GPU found in a number of those machines.

Here's just a sample of a kernel panic log that points to the faulty NVIDIA card:

Kernel Extensions in backtrace (with dependencies):          com.apple.GeForce(6.4.0)@0x82ac4000->0x82b7afff             dependency: com.apple.NVDAResman(6.4.0)@0x834a0000             dependency: com.apple.iokit.IONDRVSupport(2.2.1)@0x82fd3000             dependency: com.apple.iokit.IOPCIFamily(2.6.5)@0x7a802000             dependency: com.apple.iokit.IOGraphicsFamily(2.2.1)@0x8301b000          com.apple.nvidia.nv50hal(6.4.0)@0x83c05000->0x84019fff             dependency: com.apple.NVDAResman(6.4.0)@0x834a0000          com.apple.NVDAResman(6.4.0)@0x834a0000->0x8378dfff             dependency: com.apple.iokit.IOPCIFamily(2.6.5)@0x7a802000             dependency: com.apple.iokit.IONDRVSupport(2.2.1)@0x82fd3000             dependency: com.apple.iokit.IOGraphicsFamily(2.2.1)@0x8301b000

Here's the "official" Apple take on the issue - but the very real kernel panics need not be preceded by 'Intermittent black screen or loss of video'... in fact, you might not experience any video problems at all. Although video problems can certainly be a portent of things to come…

So what can you do? Print out a copy of your kernel panic and a copy of the Knowledge Base article and take them, along with your machine, to your local Apple Store or an Apple Authorized Service Provider. The unfortunate thing is that many people have passed the “three years from date of purchase” now and Apple is not honoring the free logic board replacement for many users. Some dealers seem to be making some exceptions for those past the three year mark, but don’t count on it…

Good luck,

Clinton