Sorry to make extra comments, but I'll just add that after installing sshfs (fuse was already installed), then mounting the remote server by creating /mnt/servername, and using 'sshfs user@servername:/path/ /mnt/servername/ -p port', I was able to use gvfs to navigate to /mnt/servername and open, edit and save the file using GVim without problems. This is both a workaround, and perhaps useful in narrowing down the problem.
Sorry to make extra comments, but I'll just add that after installing sshfs (fuse was already installed), then mounting the remote server by creating /mnt/servername, and using 'sshfs user@servername :/path/ /mnt/servername/ -p port', I was able to use gvfs to navigate to /mnt/servername and open, edit and save the file using GVim without problems. This is both a workaround, and perhaps useful in narrowing down the problem.