Update:

I was finally able to figure out why wordpress stopped working and hopefully will start posting again. For a while now, my wordpress site had been displaying

Out of memory (allocated 5505024) (tried to allocate 77824 bytes) in /home/chuangan/public_html/wordpress/wp-includes/post-template.php on line 633

error. This usually indicates a limit in php.ini was exceed though it had been set to 16M and as you can see from the error itself, the limit was smaller than 5505024+77824=5582848 bytes.

 

Turns out the culprit was in my httpd.conf. I am on a VPS and there is a setting RlimitMEM directive set in apache conf which was causing the problem.  As soon as the line was commented out. my blog starts to work again.