Lotus Notes 5.0.6 exe problem

Have a department that was recently switched to its own server. The security id’s are all pointing to their home directories. Problem: When a user signs on Lotus, everything is fine. They sign off and someone else tries to sign on and the lotus logopops up and then the application dissapears. Reinstalling does not work. Need to know if the notes.ini file(s) are the problem. Any help would be appreciated.