Hi,
I have never seen NAV abend a server due to registering a system hook. If you take a look at Novell TID 1007772, you will see that this is just an informational message. The TID does not refer to NAV but it is close.
What are you running on the server? Are you running GroupWise, specifically GWIA? I have seen corrupted emails cause a server to abend on startup....but then I have seen other items do this too. I mention email because it is the most common.
Can you provide more detail?
NAV does not load from the startup, but I know what zr was trying to say above.
This is how I would tackle it: Remark everything you possible can (except for vitals) from the Autoexec.ncf file and restart the server. If the abend does not occur you know that the cause is one of the modules you just remarked out (directly or inderectly). Then start adding things back in. If it still abends with everything remarked out, then the cause is the OS and I recommend looking for and applying the latest patches.
Lou