This week's book giveaway is in the OO, Patterns, UML and Refactoring forum. We're giving away four copies of Refactoring for Software Design Smells: Managing Technical Debt and have Girish Suryanarayana, Ganesh Samarthyam & Tushar Sharma on-line! See this thread for details.
I think you're mistaken. It may be that the value is not correct after the request went through a NATed firewall or a server in front of the servlet container (like an Apache httpd); in that case, talk to the sysadmins how you to get at the client IP.