Multisite Internal Server Error

Hi wpmudev,
Just joined your service! Glad to have your help on all my sites!

We recently set up a new multisite network for a tutoring service with several different franchises. We uploaded the theme, but are having problems with accessing the theme option as well as testing out a sample second site. The error we get is:
Server Error
500 - Internal server error.
There is a problem with the resource you are looking for, and it cannot be displayed.

Curious how we can have this fixed? Let me know what info you will need & I will get it right to you.

Thanks!
Luke