Getting an Ajax HTML error trying to delete a double post

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@Eric Distad I'm really sorry, but I think I've broken something...

Firefox crashed while I was editing a post in the forum topic:
http://fiftyninety.fawmers.org/content/let-me-tell-you-all-what-development-deal-means-long-read

When I got back in, both the pre- and post-edit versions of my comment appear. When I try to delete the first one, I get an Ajax error that starts:
HTTP Result Code: 404
Debugging information follows.
Path: /ajax_comment/24518/delete-own
StatusText: Not Found
ResponseText:
Page not found | The 50/90 Challenge
window.jQuery || document.write("\x3C/script>")
and then spits out a bunch of code.

Doesn't matter which browser I use, the behaviour is the same. Is this easy to fix?