1.This is due to they are login the computer user without the administator access right. So pls ask them to login with the administrator right.
2.Cannot Use Switch User Mode, So pls log of all the use first and login user that with administrator type.
3.If they have activate Terminal Services Server/Remote Desktop Connections, Pls unistall Interbase/Firebird and re-install Interbase and QnEFunc.dll in Add & Remove Program.
4.Please turn of firewall or open the '3050' in the firewall.