I was finally able to get 100% for case 2 of CSI - Arson.
I had gotten to 99% as some others had. The thing I was missing was in Gray's storage shed. To the right of the ladder there's a hot spot for a nail containing a thread that you have to take and then show to Greg in the lab and he states it's the same material as the rag found near the desk in Gray's house.
I have a complete step-by-step walkthrough for the Arson case only if anyone feels they need it.
That thread was easy to miss.