The University has imposed a hold that is stopping enrollment for any classes. It is a new hold that has been placed on all students and will need to be acknowledged each semester. To remove the hold, sign into your student center, look on the right hand side of the screen and click on student financial agreement. Just read it through then submit it. The hold will then be removed so you are able to register for classes.
Here's the official word: Student Financial Agreement.
I believe it actually says "Summer Financial Agreement" and in the fall it will say "Fall Financial Agreement", and so on for each semester. It only takes about 30 seconds to complete.