what version are you running? are there any addons/hacks installed?
try opening notepad and pasting this
Code:
if ( !defined('BLOCK_FILE') ) {
Header("Location: ../index.php");
die();
}
$content = "here you may insert your code, make sure you use the " (quotes) correctly";
save it as block-insertnamehere.php and upload it to your /block folder then just active it as you would with any block.