BDC`s shut downs

There are 2 servers under Win NT 4.0(sp6) in my network. PDC works as Internet gateway (with Wingate installed on it). BDC sometimes is going down? and the last tring in event viewer says something like: “There is no description for F-Secure Gatekeeper event 1001”
What does it mean, or how can I find out what is F-Secure Gatekeeper and what is the problem?