I can get the game to load, but as soon as I go to cut a tree down the game crashes. I didn't know that it was really that unstable. Thank you. One last thing is there any other way to get something like this up and working in the Ultimate mod pack?
I've removed the Voxelmods and Gregtech (complete deletion from the ultimate folder) and added Optifine D4 and Treecapitator r06. No crash, here's the console log from my last session: http://pastebin.com/MM3Ku6p0
With the information you've provided, I can venture a guess that you've added a mod or two.
A console log, and list of all of the changes you have made will aid nicely, like what I provided above!