No permission to alter properties?

Hi there

I'm the admin of a community site which i am trying to set up a phpBB2 forum on. after uploading all the files as told by the install guide through Smart FTP i now need to alter the permissions on one of the files. However, every time i try i get the following error from Smart FTP:

550 Could not change perms on config.php: Success

i am the admin and am signed in on the admin account, so any ideas why its not letting me change the perms??

Thanks in advance

Well, you are not running on a Windows server, are you? Moreover, please *always* post the log & system information if you have issues with SmartFTP.