I'm running a wp-multisite install with ~100 blogs. I recently discovered a blog that I can't post a comment to (though I've been able to previously). When I try to submit a comment, I get the following warning dialog:

When I press send "send" I get an the comment field looks like this:

And nothing ever happens. I'm able to post comments to other blogs on the wp-multisite without problems, and this happens even when I'm logged in as superadmin.