.DOCX cannot be opened

Greetings,
Our facility uses Office 2003 with a couple of 07 installations for

testing. We occasionally receive Word 07 documents in .docx format

which we cannot open using either 03 or 07. Error message is:
“The Office Open XML file *.docx cannot be opened because there are

problems with the contents.” Pressing the Details button reveals:
“Microsoft Office cannot open this file because the .zip archive file

is an unsupported version.”
(The documents have not been sent in zipped format as far as I can

tell)
Attempting to have Word 07 repair the document fails. Trying web-found

suggestions regarding selecting the document and choosing Open and

Repair or Recover Text From Any File fail also.

Thanks for any assistance.