I have an installation of Magento 1.9.2. I am using a custom theme, and anytime I try and place an order it kicks off the Ajax on the page and then stops with no error messages, but does leave a log:
ERR (3): User Error: Some transactions have not been committed or rolled back in /html/lib/Varien/Db/Adapter/Pdo/Mysql.php on line 4039
I have spent 2 days trying to get to the bottom of this with no joy. It doesn't matter what payment method I use its always the same.
You should try to log all MySQL queries to see what wrong here. lib/Varien/Db/Adapter/Pdo/Mysql.
Open the file
lib/Varien/Db/Adapter/Pdo/Mysql.phpand change the value of the protected property$_debugtotrue. You can also change the value of$_logQueryTimewhich is especially handy when debugging slowdowns. Once you make this change all queries will be logged in the filevar/debug/pdo_mysql.logHope this will help you. Please put your corrupted query here if you fixed it.