It can happen for a variety of reasons. One is a high load, for example a lot of people logging on all at the same time.
Also, NWN is not without its bugs.
In addition, we rely on NWNX which is a necessary evil and which has its share of known memory leaks.
And in truth, Bioware never really intended for NWN to run for great lengths of time continuously. Persistent Worlds were just not on their roadmap when they developed it, and as such, it was made to be "stable enough" for solo and multi-player module play.
So really, we're forcing NWN to do things it really doesn't want to do. I'd crash too in such cases.
