Can't open attachments in OE6

All of a sudden, for no reason, I'm having problems opening attachments in Outlook Express 6. When I double-click, or right click on the attachment to open it, I get the error message; "The Command Failed to Execute ". If I right click and save the attachment in another file it opens normally with no problems from there, just not in OE6. I've checked all the settings under options, and none of the settings have changed. I have plenty of free hard drive space, so that's not the problem. I don't get this message everytime, but I get it more times then I don't.

Any help you can give me would help. This problem just started out of the blue a couple of weeks ago.