Cisco logging facilities

I have a Cisco AS5200 running IOS 12 set up to log using TACACS+ (e.g., when a user wants to access the Internet, they are challenged for username and password).

The log files used to resolve, it seemed to me, but no longer do; now they just output IP addresses.

The company wants to know what sites these people are visiting, but the IP addresses are “less than useful.”

I cannot recall how to make these resolve. Ideas?

Thanks.