Usually that means the query failed to process for some reason, such as a SQL syntax error. Try this to get some debug info:
$sql = "SELECT * FROM BET_Data WHERE `GameID` = $GID";
$result = mysql_query ($sql);
if($result == false)
{
die(mysql_error() . "<br />\n$sql");
}
Once debugged, change the die() to something more "graceful" that does not output database details to the browser.