My WordPress is current (3.3.1) and my PHP is semi-current (PHP 5.3.3 – built: Feb 2 2012 23:47:49). All of the plugins listed below are current as per WordPress. I have disabled each plugin individually, and the only plugin which causes the issue is Post Avatar. With Post Avatar enabled, clicking on the “Upload/Insert” button in Edit Post or Add New Post fails to do anything. Disabling Post Avatar allows the button to function again.
Here is the list of my plugins:
Akismet Version 2.5.5
All in One SEO Pack Version 1.6.13.8
Contact Form 7 Version 3.1
Easy Admin Color Schemes Version 4.1
Hello Dolly Version 1.5.1
Jetpack by WordPress.com Version 1.2.2
Post Avatar Version 1.4.3
Postie Version 1.4.3
Really Simple CAPTCHA Version 1.4
Scissors Version 1.3.7
WP-Cumulus Version 1.23
WP-DBManager Version 2.63
WP Security Scan Version 3.0.9
WP_Identicon Version 1.02