problem with thumbs pics

[Punktured]

it would depend on your host and what user interface they use.

some hosts allow right clicking to see an option for it, some have "info" which once clicked shows permissions. its different for certain hosts.

if your using an ftp program like filezilla its as simple as right clicking the folder and going to "Permissions".

also, i notice that the file path you provided earlier, /img/.htaccess

your /img folder has a htaccess file?
that may be restricting things, try renaming that file temporarily, clearing your cache files manually from /tmp and re-check.

keep the htaccess file tho, just incase its needed at a later date.