Why am i getting this error? WordPress database error: [Query was empty]

I saw on here one other guy was having problems with $wpdb->prepare. Am I using it incorrectly?

As you can read in the Codex, it’s a simple No.

You have to use it like sprintf/printf(). The only allowed inputs are

• string: %s
• digit: %d

Example

$sql = $wpdb->prepare( 
     "
        INSERT INTO %s
        (`post_content`, `imported`)
        VALUES %s
        ON DUPLICATE KEY UPDATE imported = 1
     "
    ,"{$wpdb->prefix}bugtbl_temp"
    ,implode( ',', $values )
);

Disclaimer: The ↑ shown query, doesn’t necessarily mean that it will give you results, just because you then used the $wpdb->prepare() right.