RPM Install On RH7

[chi]

Can someone please help me figure out why I can't get any user on my
system to login to IMP. The login page loads on my browsers (Netscape
4.7 and IE5) but when I try to login, I get the following message:
"Either you have logged in incorrectly or
your login has expired. Please login again." I'm not sure what to do
next because everything else seems to be working properly. My system
config is as follows:

Red Hat Linux 7.0
Php 4.0.3pl1
Imap-2000-3
Postgresql-7.0.2-17
Horde-1.2.4
Imp-2.2.4

Any help will be greatly appreciated. Thanks!

Chi