FTP No Write Access to images folder

I am trying to upload a standalone .jpg file to...

xxx.xxx/webspace/siteapps/29473/htdocs/wp-content/themes/atahualpa/images/

and I get an error message:

================================================== ==============================

FTP FOLDER ERROR:
An error occurred copying a file to the FTP server. Make sure you have permission to put files on the server.
Details:
200 Type set to I
227 Entering Passive Mode (78,153,215,204,161,97)
550 header4.jpg: Permission denied.

================================================== ==============================

I have tried to change the attributes of the images folder from 755 to 767 using my LeechFTP program, but it will not allow any attributes to be changed...

Needless to say I'm stumped!