I'm running windows NT and excel 97

When I debug my code and get to a nitty gritty bit, Excel
often shut down (losing my work) and the message below is
displayed.
Can anyone tell me what this message means and how to
avoid it in future?

since I can't paste it here I'll type it out.

Title: Dr. Watson for Windows NT

Message: An application error has occured and an
application error log is being generated

EXCEL.exe
Exception: access violation (cryptic number)