Can't login to Horde web interface upon initial install

[Advrk Aplmrkt]

Hello, total newbie question:
I've just installed Kolab 2.2.4 in Scientific Linux 6 (based on RHEL),
and the installation showed no errors.
I logged into https://[domain name]/admin and setup a new user via
Users->Create New User, and created passwords, uid, etc.
However, when I try to login to Horde via https://[domain name]/client
I get the following error:

"Login failed because your username or password was entered incorrectly."

What did I do wrong? I would appreciate anything specific as I am
really very new to all this. Thanks a bunch!