UPDATE [22 Sep / 18:58]: Thanks to Varun's experimentation, the problem is fixed.  Go ahead, post as many comments as you want now...  For some reason, whenever a http:// specifier was present in any of the text boxes in the form, it wouldn't get passed.  So Varun wrote a small script to take out the characters even if they were present.  So that fixed the problem, and the upside is that there is no difference in the way users interact with the site.

There's been a weird problem the past few days on the site — that is, the inability to post comments!  This really is an irritating situation, more so, because I am not sure where exactly the problem is (going to have to try debugging tonight).

Any comment on this site is captured in a form which sends the data to a PHP script via the POST method.  For the past few days, any attempt to do this results in a HTTP 403 error, and the form doesn't get submitted.  This is strange because the same script has been working fine for over a year now (and works on the local computer just fine).  I thought it was a permissions problem, and changed permissions on the script, but that didn't work either.  On raising a helpdesk ticket on my host's site, I got a response saying that it is a scripting error, as the script was accessible through the browser.  And yes, if you try that, it does work, which leads me to think that there is some problem with submitting POST data.

After coming home from work tonight I am going to try to handle the form via GET and see if that works (most likely, it will — but it's not a good way of doing things).  I'll also try uploading some dummy forms and try to find out what exactly is causing the problem.  It seems like such a simple thing, but as of now I can't figure out what is wrong (the installation of phpMyAdmin on the site, which also submits POST data to PHP scripts works fine).  If anyone reading this can help me out on this, it would be greatly appreciated!  In the mean time, please bear with this bug.

Oh, and the response I got on helpdesk ticket advised me to "contact the programmer of the site", which is funny considering that I am the programmer...