Mprexe-not responding on Win95 System!

After I successfully log on to my Win NT network after Login script I get an hourglass that just hangs the system and when I hit Ctrl-Alt-Delete in task mgr I get Mprexe-not responding!The only way to get out of this is to hit the power button off!What is causing this & how do I go about fixing it??It happens on several 95 workstations!Thanks!