I have just found a flaw in either Office 2010 or in BES Express 5.0.2.
We have a client who is having a tough time opening word 97-2003 compatible .doc documents on their 9780 BB's. With a little testing we were able to figure out that if you save an old or create a new Word document using Office 2010 as saving it as a 97-Word 2003 .doc file and try to open it in your blackberry or through the server configuration test attachment service it will fail saying "the file format is not supported." However if you create a new document in Word (Office 2007) and save it as a 97-Word 2003 doc you can open it on your blackberry an in the Test Attachment Service.
I am sure there will be a lot of finger pointing going back and between MS and RIM!
A.