Blank screen in admin

I went to backup my blog on Monday night, something froze while it was being done and now I cannot get to my admin area. The blog is up (but only when entered without www.) so the site I am working with is http://www.cmsmithportraits.com/blog but cmsmithportraits.com/blog is the only link working now. What could have happened to cause this? the backup was incomplete, I think, so I am afraid of restoring it from that. I do not understand code, so I need help in the simplest of forms. How do I restore access to the admin area?