NTbackup troubles.

When I try and execute ntbackup from command line or from the start menu. It starts to load the program but the GUI interface does not put up on my screen.
Background info: Win nt 4 server sp6.
I’ve used the “AT” command in conjunction with a batch file to execute ntbackup/backup service to backup my whole drive. If I bring up Task Manager, I can see the “backup” service running.
I’ve managed to correct this problem with a reboot of my server, but the problem keeps re-occuring.
That is the backups work, then the whole process stops after about a few days. And when I try to do the backups manually daily, I can’t get the gui front end to ntbackup to laod up.