For what it's worth, I'm having just the same problem attaching any file using this this function. Mail.app opens a new message with the subject indicating the file is attached, though no files are attached.
1. Mail.app in Mountain Lion
2. jpgs. PDFs. I've tried a number of files and can duplicate it every time.
3. Yup. Two errors every time:
4/23/13 11:24:39.399 AM sandboxd[52725]: ([52579]) Mail(52579) deny file-read-xattr /Users/docpete/Dropbox/Public/checkbox.jpg
4/23/13 11:24:39.416 AM sandboxd[52725]: ([52579]) Mail(52579) deny file-read-data /Users/docpete/Dropbox/Public/checkbox.jpg
You'll notice in the error logs that I've used files in my Dropbox folder. I've tested this with files on my desktop, too -- same results.
Thanks in advance!
