Multi-Site White Screen

Hi All: I am having some trouble activating multi-site. My problems started when I was messing around with the DB through phpmyadmin. I think I removed some files in error. After realizing what I may have done I created a back-up. Then I reinstalled Wordpress from scratch. Once installed I imported the old DB into the new one created.

Then I reactivated multi-site as I usually do. Suddenly I am getting the white screen of death on all login pages and some public pages. E.g. http://www.galearning.com/category/marketing-tips/

Any Ideas on a logical troubleshooting path?

Thx

Rob