Account reconciliation caused Sage 50 to crash. Why?

SOLVED

I just hit "Post" on an account reconciliation, and Sage 50 up and quit and gave me the following error message:

Does anyone know what this means, perchance? How do I avoid this happening in the future?

For what it's worth, I have since started Sage 50 again and it seems to be working, that is, it appears the account reconciliation went through okay when I hit the "Post" button and so fortunately I did not loose or corrupt anything.

Thanks!

Kristine