When I choose the "browse server" option to find an attachment, the media manager returns the wrong path for the file. Then of course the file can't be found for viewing or downloading.

The incorrect filename is given in the error message when I try to Save (example is a file I had already uploaded via FTP):

JFile::copy: Can't find or read file /home/[sitename]/public_html/public_html/media/k2/attachments/[filename]

on the backend, same thing.

I don't know exactly what the path should look like--I would have thought "media/k2/attachments/[filename]"--but you can see why this will never work.

I haven't changed the default K2 path for attachments.

So, how might this be fixed?

Thank you. The problem lay in Joomla's Media Manager path as you suspected. Fixed!