Ubuntu FTP fails to get/mget file for “not found” but !ls sees it

Question

I am using the ftp client on Ubuntu 10.04-64. After connecting and navigating to my upload and source destinations, I can

!ls a-long-filename

and even

!ls a-long-filename-fragm* 

and both find the files I want to upload.

However, when I

get a-long-filename 

or

mget a-long-filename-fragm* 

both return to the ftp> prompt without doing anything.

I have managed to upload other wildcard files from/to the same place using

mget a-different-filena*

Why can ls see the files but get/mget cannot?