Can't Open Attachments in OE6
Upon first use, OE6 defaults to not allowing you to open attachments because any attachment has the potential to be a virus or trojan. However, this also impedes your ability to get at valid email attachments.
To allow attachments, simply go to "Tools" > "Options" > "Security" Tab. Uncheck the box that says "Do not allow attachments to be saved or opened that could potentially be a virus", and hit OK.
You should now be able to open attachments. A word of caution though: just make sure the attachment is from a known sender and that you are expecting it, or the sender mentions in the email what the file is that s/he is attaching.
Just because the attachment may be from a know sender doesn't mean they aren't infected by malicious software that is sending out false emails with bogus attachments.