I'm ot sure if it's due to the many hacks I had in 1.3.1--I've removed most of 'em because the new fupdates in 1.7.1 address the spammers and such.
Anyway, when I have the 'force preview' checked yes in the configuration, comments won't get posted. When the preview or post buttons are clicked, the page displays as if to preview, but then when the 'post it' button is clicked, the same preview page is displayed. However, when force preview is off, and the post it button is clicked, the user is prompted for the security password and, once entered, the comment is posted. I have removed the preview button from the comment template, and therefore have removed that issue. I'll try to investigate more later. btw, thanks for this spiffy update to my favourite blogging software!!