Attached Word document won't open

Last spring we installed Office 2007. We have recently discovered that when we send Word documents attached to emails, the recipient can't open then. They get a message saying there are problems with the contents or the file is corrupt. At first I thought the problem might be because the recipients have an earlier version of Word and might need that Office Compatibility Pack. One of the recipients having the problem, however, has Word 2007. In fact, they bought the copy we are using (it came with three licenses.) I also tried emailing the document in question from my wife's email account to mine, all on the same computer. It still wouldn't open. I took care of the immediate need to get that document to some people by converting it to a pdf using Cutewriter, but I am wondering why this problem is happening? Any assistance will be appreciated.

 

OK, now today, the documents in question seem to open, at least when I email them back and forth from our own email accounts. I guess if it isn't broke, don't fix it.

Thanks.