http://xxrazorxx.freelinuxhost.com/ is my site address.

Problem : Want to shorten the address of my site but when the site is accessed through one of my re-directories, www.ripimmortals.tk or www.ripimmortals.cjb.net , users are unable to login. When the user name and password are entered, it just takes them to the user information page, doesn't actually log them in. Help is apreciated.

Redirect services do not work with PHP-Nuke.
The REAL Nuke url needs to work in order for PHP-Nuke sites to function.
One of the many disadvantages of free hosting.
There was an ongoing discussion about this at nukecops.com I believe.

Any way I can beat the system?

Not that I know of

I remember when i was messing with cjb.net that u can use the Dynamic DNS function they have to add your current host ip so it will redirect to that ip, then add the cjb.net domain to your DNS entries to your current account and you will be able to use it as a normal domain.
But as i see you are on a free hosting service and i don't think they let you mess with their BIND daemon.