Wierd OWA problem. Some users can access

I have have a weird problem with Outlook Web Access on exchange 5.5.

Problem:
Some people can access the site and some people cannot. Might be a browser issue. On one machine with IE5 he cannot log in but if i start up aol he can logon on toowa. On ie5 gets a page not found.

Port 80 is open on pix506 firewall

Exchange 5.5 and OWA intall on win2k server.

Has anyone ran into this problem? Any help would be greatly appreciated.

Daniel