OWA Problem

I have a exchange 2000 with outlook 2000,I am using OWA,except one user everybody else is able to use OWA, I checked his HTTP is enabled, Checked all the permissions and rights, it has same as other… when I type the url, it says Page cannot be found.Error code 404.
Plz help me out where do I check for the solution. I have been struggling since 2 days. I m not able to find the problem.