Nope.
The cross-listed courses are those that it's more common for undergrads to take, or those that are required for both undergrads and grad students, but you're free to take any course you want. Officially, you have to have the permission of the instructor for many grad classes, but I've never heard of someone being denied because he/she was an undergrad.
I took a grad-only class when I was a sophomore. I learned a lot, and as a bonus, often grad classes are highly grade-inflated.