When using mail.app with google mail (google premier apps) over imap, i have a problem where e-mails come through without showing attachments sometimes.
The odd thing is, if i look at the "All Mail" sub-folder under the "Gmail" folder(shows up further down the left side column of mail.app), the e-mail is in there and shows the attachment. Why is it then that when the e-mail is in the apple mail "inbox" view, it doesn't show the attachment?
I do have the setting in Preferences -> Accounts -> Advanced -> "Keep copies of messages for offline viewing" set to "All messages and their attachments" too. So it should be working.