Document Download via PPTX

This is strange, wonder if anyone else has come across it...

 User put a link to a sitefinity document into a pptx. When you click the link fiddler shows me it 302s the user over to login...even though they are logged in.  To validate I can just change the url to be the site root and it loads (protected site).  If I then take the url itself and paste it into the browser...it loads.  If we convert the pptx to a pdf and click the link, it loads...

 What would cause a link ONLY from a pptx to react differently, any idea?

On the 302 the user agent is msoffice
GET www.domain.ca/.../doc.pdf HTTP/1.1
Accept: */*
X-IDCRL_ACCEPTED: t
User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.2; Win64; x64; Trident/6.0; .NET4.0E; .NET4.0C; .NET CLR 3.5.30729; .NET CLR 3.0.30729; .NET CLR 2.0.50727; ms-office)
UA-CPU: AMD64
Accept-Encoding: gzip, deflate
Host: www.domain.ca
Connection: Keep-Alive
Pragma: no-cache

But in the browser it's firefox (or whatever)...and direct in browser works

GET www.domain.ca/.../doc.pdf HTTP/1.1
Host: www.domain.ca
User-Agent: Mozilla/5.0 (Windows NT 6.2; WOW64; rv:19.0) Gecko/20100101 Firefox/19.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate
Cookie: ...
Connection: keep-alive


  **EDIT** Found the problem, office doesn't share cookies
community.jivesoftware.com/.../DOC-32157