Help Needed

Hi everyone… I started Blending in Nov of 2011. I am still a noob but have a solide handle on Blender etc…
I have spent 2 weeks and a little creating, modeling a huminoid robot., lots of detailed parts, definately not the best out there but I am very proud of it thus far.
THE PROBLEM: when I try to to simply add material (simply using blender diffuse color), BLENDER errors out and also when I attempt to render a image of the model, BLender Errors out. This has never happened to me and I can find no clear cause… ANy HELP would be fantasitic.