Ok, so I'm getting the below error whenever I try to use a trackback to my site, using either http://www.cooklocal.com/MT/mt-tb.cgi/27 (which is on every post) or http://www.cooklocal.com/MT/mt-tb.cgi?tb_id=27 (which I found on an old thread). Running version 3.34. Not even sure where to start. Suggestions?

<response>
<error>1</error>
<message>Trackback pings must use HTTP POST</message>
</response>

Are you actually attempting to send a TrackBack ping, or are you simply browsing to the URL you've noted (the first is correct for newer versions of MT).

f you are simply browsing to the URL you've noted, seeing the message you've noted (the XML response) isn't unusual, as this is the URL to ping, and is not intended to be viewed in the browser - it is used to send the TrackBack from another side, and used by Movable Type internally (via an HTTP POST request). In the default Movable Type 3.x templates, these links are not clickable, to avoid any confusion for your readers.

That URL is used by someone sending a TrackBack to the entry it is associated with, by placing that URL in the "Outbound TrackBack URLs" field when they are saving their entry. So, you could see an error when browsing to the URL directly, but otherwise receive TrackBacks correctly. Are you seeing an error when attempting to send a TrackBack ping in that manner?