Did the document you saved down to 97-2003 contain any macros?

Runtime errors are usually caused by a macro or an add-in. What is the exact error message?

I'm running Vista and Word 2007 without any problems. I also share Word documents with others running earlier versions without problems.

People don't like "change" and there is a huge change in Vista and Word 2007. You have to be prepared to accept that -- just like any other new software you need to learn.