Problem with netpbm chmod error?

I’m using 4images and netpbm to set up a gallery, and every time I try to use the auto-thumbnailer I get an error, saying that it’s been disabled for security reasons. That would imply that there’s a problem with the permissions on the folders where the images are to be created, right? So when I try to chmod the thumbnails folders to 777, I get an error message saying “Operation not permitted; chmod failed. It may not be supported on remote site.” Does anyone know why this is, and if it is a problem with how my dreamhost settings are set, how I can fix it? Thanks!

If I recall, by default there’s some restrictions on using php for writing files. I think the fix is to run php as a cgi.