Have you tried cannot open a attachment in Outlook?
There may be occurs by too many same file name in SecureTemp folder.
Outlook will automatic save a copy in SecureTemp folder when you open the attachment.
When you try to open the attachment with same name in Outlook, Outlook will create a copy in SecureTemp folder and add the number behind the file name (e.g. abc (1).doc, abc (2).doc....).
If there a more than 100 same file name (e.g. abc (100).doc), you will not able to open in outlook,
so you have to find out the SecureTemp folder location and delete the file.
Find SecureTemp
At start menu, Run, type regedit to open the registry editor.
Browse to this key:
HKEY_CURRENT_USER\Software\Microsoft\Office\xx.0\Outlook\Security
OutlookSecureTempFolder value
(Change xx to reflect the version number of Outlook. 14.0 = Outlook 2010; 12.0 = Outlook 2007; 11.0 = Outlook 2003 and 1.0 = Outlook 2002.)
Double click on OutlookSecureTempFolder to open the value then copy the path. Paste it into the address bar of Windows Explorer to open the folder.
This folder is normally hidden by the file system.
Ref: http://www.slipstick.com/outlook/securetemp.htm