This is usually the result of not setting the compiled templates directory to be writable by the web server.

To correct this, set the "var/templates_c/" directory (within your Lore directory) to world writeable. Most FTP clients will allow you to do this - just give the "other" or "world" group write permission on the directory. Otherwise, you can telnet/ssh into your account (if available) and perform the following command (from within your Lore directory):

chmod 777 var/templates_c/