SPX listener on NT goes down constantly

I have a NT 3.51 server running Oracle 7.2.2.4. It works very well except for the SPX listener goes down constantly. I first tried to use one listener to listen both TCP and SPX. The TCP part worked all the time. But the SPX part worked when I first started it and after a while it went down. I then tried using a separate SPX listener and it behaved the same. Does antbody have these kind of experiece?

-- 
Bo Lu
Senior Programmer/Analyst
Hospital and Clinical Informatics, U. of Utah
801-581-5964, bo.lu_at_hsc.utah.edu