BOAC, you may have something like a virtual server, especially if you aren't paying much: "your" machine may be shared by hundreds or thousands of other websites, and the hard drive is simply full. Alternatively, your allocated space is full. Presumably you have a control panel or similar web interface which will tell you how much of "your" space you are actually using. If you can't FTP, etc., and yet you apparently have plenty of space available, then the underlying physical device is full.