This object is corrupt or is no longer available error in Word 2003 (no Norton AV installed)

I have an end user who is creating a very large 10Q document in Word
with many embedded excel tables. After the objects have been embedded,
she gets the Object is Corrupt or is no longer available error.

I've looked through and they try to blame Norton
AV, but we are not using that nor have we ever used that product (has
never been installed on the systems either). I've also seen numerous
posts saying that Norton is the culprit, but I know that it is not in
this case.

Does anyone have any other suggestions or recommendations?