Image transfer failing

I am able to transfer all files except image ones, whether JPEG or GIF. I get the following mesage in the log:

[18:50:45] SIZE 20060621.jpg
[18:50:45] 550 Can't check for file existence
[18:50:45] File size check (SIZE) failed. File not found or permission denied.
[18:50:45] PASV
[18:50:46] 227 Entering Passive Mode (66,220,2,7,131,195)
[18:50:46] Opening data connection to Port: 33731
[18:50:46] STOR 20060621.jpg
[18:50:46] 150 Accepted data connection
[18:51:26] Transfer Timeout (40s). Closing data connection.
[18:51:26] 8192 bytes transferred. (206 bytes/s) (00:00:39)
[18:52:06] Timeout (40s).
[18:52:06] Active Help:
[18:52:06] Client closed the connection.
[18:52:06] Transfer failed.

The image is then seen as transferred, but the filesize is 0 bytes and the file does not show up on the site. The help link offered in the log leads to a broken page.

Any help would be appreciated!