Unable to open attachments in Outlook

I am having a issue on 3(out of 50) of the systems in our office. Two are running outlook xp and one is running outlook ’07. All three of these users are unable to open or save attachments in their e-mail. They do not receive any error message or “blocked” message. The attachments are most often .doc, .docx, .xml, etc. files. The security setting are configured to allow them to open attachments. On the Outlook ’07 system, the user can click ‘forward’ and then be able to open excel docs, but not any other attachments. I have been unable to find any solutions to this elsewhere. Does anyone have any suggestions of how to fix this or where to find a solution.