Cannot open rtf attachment in Outlook

I have a user that has winXP(Virtual box) and Outlook 2007. He receives reports from outside salespeople in rtf file format. Up until last week he could open the rtf attachment in Outlook. Now it is giving him an error msg to the effect ".... check your rights in the folder you are trying to open the file in". He has local admin rights. I have tried to open with notepad, WORD - will not open and even if you try and save it - it gives the same error msg: "Unable to open file: right click on the folder you are trying to open the file in and verify your rights". The "sender" of the email is using a Crystal template and then the pgm they use puts it in rtf format and then they email it. Any ideas, I have tried a bunch of diff ways. Says nothing has been added to his computer.