I found this answer.

The reason this is crucial is that too high an intensity can actually be disastrous with scrypt because it CAN run out of ram. High intensities start writing over the same ram and it is highly dependent on the GPU, but they can start actually DECREASING your hashrate, or even worse, start producing garbage with HW errors skyrocketing. Note that if you do NOT specify an intensity, cgminer uses dynamic mode which is designed to minimise the harm to a running desktop and performance WILL be poor. The lower limit to intensity with scrypt is usually 8 and cgminer will prevent it going too low.

Source: http://bitcoin.stackexchange.com/questions/11514/cgminer-litecoin-mining-generates-invalid-nonce-errors

To me this answer is kinda crazy because I am running 2 7970 with 6Gig NVRam Yes I know they are a waste but the explanation that they are running out of ram kinda makes me laugh.