dreamweaver site problem

Hi all -

I have a client I created a site for in DW4 a couple of years back.
Recently, I've been in and changed some things using MX2004... all fine.

However, on site they still use DW4 and whenever they try to open the site
files now they either receive error messages (often concertning mno files)
or (More often) Dreamweaver gets shut down completely

any ideas ? suggestions or - even better - solutions?

matt