Symantec tells me my site is a known intrusion attack

I'm uploading password protected Word docs on to my site.  Three of the four I have already uploaded have generated a security alert from Symanetec meaning I can't open them when viewed on the website.  The only one that is Ok was the first I uploaded some days ago.  The settings for all are the same.

The Symantec message says "Network traffic from [name].web.officelive.com matches the signature of a known attack."  It shows the risk of attack as high and automatically blocks the download of the documents.

The documents are of personal information which is why they can only be opened by those knowing the password.  Its for a school "cyber-reunion".

Other documents which are not password protected open normally..

As I hope to add several more password protected docs,  any advice in how to overcome this problem would be much appreciated.