Hi Relentim,

There is a list of fixed issues in the following article:

Release notes for Symantec Mail Security 6.5 for Microsoft Exchange
Article: TECH122809 | Created: 2010-01-28 | Updated: 2011-09-22 |
Article URL http://www.symantec.com/docs/TECH122809  
 

Specifically:

Resolved Issues

6.5.6 -- Build 6.5.6.268

• 2481362 - Microsoft Office 2010 File is Unscannable With Error Message: "Decomposer failed to open the container. at location printerSettings1.bin within printerSettings"
• 2381312 - PowerPoint Documents Called Unscannable by Symantec Mail Security for Microsoft Exchange (SMSMSE) 6.5.5 with Decomposer Result 0x11
• Several important defects were fixed in the KeyView filter component used by the attachment content filter module

That last one is a key reason to upgrade to 6.5.6.  Earlier releases of SMSMSE were vulnerable to "Multi-Vendor Autonomy Verity Keyview Filter Multiple Issues" --- see http://www.symantec.com/business/security_response/securityupdates/detail.jsp?fid=security_advisory&pvid=security_advisory&year=2011&suid=20111006_00 for details!

Please update this forum with any additional questions, or feel free to mark it "solved" for the benefit of future visitors. &: )