Problem installing -- need help/advice

Hi,

I just tried installing punBB. When I thought I had finished, I went to http://mydomainname.com/upload/index.php and received this message:

Unable to write configuration cache file to cache directory. Please make sure PHP has write access to the directory 'cache'.

Upon seeing that, I tried to CHMOD the permissions in my cache folder, but I kept getting an error message:

500 'SITE CHMOD 777 cache': command not understood.

And the permissions wouldn't take. I tried with a variety of other permission combinations (775, 700, etc.) and nothing works.

I am using Smart FTP v1.5 to upload, and my host is GoDaddy.com. Has anyone encountered a similar problem, and, if so, can anyone give me any advice?

Thanks...