Actually, 755 is the standard CHMOD of folders. The only way to get a folder or file writeable by the Wordpress backend is to CHMOD to 777.
this is what I did - open up your FTP Program and load your site (log in) and simply right click on the "wp_content" folder say for example and go "properties" and then check 'write' or 'writable' or just change the CHMOD to 777 FROM THERE. hope this helps!
Thanks. One thing though. I cant leave it at 777 after I have done my work. Actually I need to cmod to something that can stay.