I just installed a new texture pack and Minecraft 1.8.2-pre4 crashed. I tried with 1.8.1 and 1.8. It didn't work it says "Out Of Memory". I "cleaned" the memory and i tried again.... The same thing!!!
I expected that it would work... NO!
Steps to Reproduce:
1. I downloaded Sphax texture pack (http://bdcraft.net/download/?z=Sphax%20PureBDcraft%20512x%20MC18)
2. I selected the texture pack, my minecraft crashed
3. Now i can't open it again (i know i have to remove the texture pack and then it will work)
The crash is in the description...
Try a smaller pack. You need a really powerful computer to even run 512x texturepacks.