Disabling the Cookies for Comments plugin broke the comments form.
On the recommendation of Matt Cutts, I added the Cookies for Comments plugin to this blog, and also added their recommended .htaccess modifications:
RewriteCond %{HTTP_COOKIE} !^.*XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX.*$
RewriteRule ^wp-comments-post.php - [F,L]
When I realized that Cookies for Comments was slowing down my blog considerably, I disabled the plugin, but did not think to remove the .htaccess rewrite rule. The remaining .htaccess rules broke the comments on this blog (for two weeks now, could it be!?).
Comments are up and running.
Now that I’ve removed this code from the .htaccess file, comments are once again working – sorry for any inconvenience! I hope this helps others avoid frustration as well.
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Katz Web Services is a 
{ 2 comments… read them below or add one }
Hey Zach, I did the very same thing but in my case it only took me a week to figure it out! I couldn’t for the life of me figure out why no one was commenting when the day before there was so many! BTW, I used to live in Arvada, and about 12 other cities in CO and my kids still reside in Ft. Morgan. It’s a beautiful state!
Hey Zach, Thank you for sharing the solution of WP error. I have found another solution on this post here: http://kpobuddy.wordpress.com/2009/11/02/nothing-found-for-wp-admin-post-php-error-on-wordpress-blog/