Without any details there's basically no way to help you here except writing "ask the Ntreev staff".
Please provide:
- The version number of the executable you use (would be great if you could also state whether it's fasa2008's, bubbastic's or some self-hexed executable).
- The font you use (original TH font or did you modify the executable to use the GB font for western/BR characters?).
- Do you use any custom or imported items on your client?
- Is the error reproduceable? How do you provoke the crash?
Also, for the sake of providing as much unbiased details as possible, please run the game in windowed mode (i.e. 1024x768) to ensure you'll see error messages (if there are any) popping up.
Without any description of how the crash manifests itself (application just closes, throws an error message, freezes) it's hard to tell what goes wrong. If you have a second machine, you can also try to RDP into it during a crash to see whether it's really a crash in the operating system (as you describe it) or just a game unwilling to let go of it's focus. In windowed mode you can at least kill the game via the taskmanager.
If you use a non-TH font, there's a good chance the game will crash because some of the dialogues in the game are hardcoded into ProjectG, causing non-TH fonts to go haywire and the game to freeze.
In case you're using the original TH font and the game closes whenever a certain player makes an appearance, it'd be a fair guess to say you're missing some models.
But again: Without knowing the specifics of how the problem manifests itself, there's little we can do.