Undergrad CS programs vary greatly. So I would suggest having a look at recent course descriptions for the degree program and recommended books.
Having lots of programming experience in Java, C#, PHP, etc will not be of much value unless you understand the underlying paradigms and concepts.
In most general terms, you'd at least need to know "Algorithms and Data Structures", the SICP book cover to cover, some LISP, C programming, basic operating systems, compilers, interpreters, discrete math, logic and a bit of digital electronics.
I'm intrigued as to how you got into a graduate program. Did you present an impressive background? Care to mention which Uni?? It's a throwaway account, so it can't be tracked back to you!