Virus Detected for clean PPT file when using show.zoho.com

Virus Detected for clean PPT file when using show.zoho.com

Hi,

I have an old PPT file that failed when trying to upload and edit it using show.zoho.com.  The error returned by zoho was

RESULT=FALSE ERROR_CODE=3847 WARNING=Virus Detected.

I scan it using my virus scanner and found no issue at all.  However, if I opened and closed (without any modification) the file using PowerPoint 2010 then the same file will be edited OK by Zoho.  Look like PowerPoint 2010 automatically convert the file to newer version and that new version is workable by Zoho. 

Please advice, thanks.
Chung

P.S.  I tried to upload the sample file but don't know if it's successful.