First, I'd recommend posting this in the
Mining Support forum. It will probably get moved there anyway.
Second, try checking out the
Windows Event Viewer. It may have information on the application crashes that would help the author of bfgminer (or other fellow users) help you out. You could also try reporting this directly on the
bfgminer thread.
Finally, I think most experienced miners will tell you that even cgminer and bfgminer crash from time-to-time. There are a few application for mining that handle this by watching the mining processes for you and restarting when needed. One such app is
MultiMiner (one of my apps), which you can read about
here.