Serial interface? Whats on the other end?

If its (say s0/0/0) to another serial interface you need to make sure you have an IP and issue the no shutdown on the interface of the other device too.

 

What interface are we talking about here? What are you connecting this interface to? There isn't enough information to go on. You need to post up the results of a: show interface [interface name] and a show run interface [interface name]

Also, you don't need to configure an IP address on the port to bring up an interface. This problem is strictly a layer 2 issue.