maybe someone know how to fix this

Hey guys! I'm having some issues with an aplication and though that maybe someone here could help me.

I'm running an aplication that uses 17-20 different databases. It was created using FM 6, it is running on a windos xp os, using a filemaker server 5.5.

the application is opened using a "start_up" scrip which initializes the file to verify the user. the application verifies the user by pulling information from a "users" database, and comparing to entered information.

My problem is that if someone is logged into the databases, and someone else goes in, the system can not figure out what is going on..... o.k., let me see if I can explain this a bit better. the first screen that loads after an user is verified, is an "index" page where the user decided what the want to do. In this screen the name of the user is displayed (it goes to the user db and read which "actual" name is associated to that particular username, and displays that info.) when someone else logs on (with their unique username as password), the new user display the correct information on its screen, but one the screen of the user that was already logged on, the name changes from its own to the name of the person that has just logged in. This has becomed a big problem, becuase the system go into infinity loops and multiple error messages most of them involving "you can not make any changes to this record because some else is using it".... and even worse, when one of the user navigates the different layout of the program, the other person screen changes as well : :

does anyone knows what the problem might be, and what I could do to solve it?:

thanks in advance