Recently i just migrated a VirtueMart website to recent version of Joomla and VirtueMart, once reviewed an old orders, found the shipment name of an order was not showing in details page, then looked into the code and found there was limit issue. By default VirtueMart has an option to set Backend default items per list view in configuration section Templates tab, and configured to 15 which is used to limit the shipping methods list, but the required shipment was in 24th position, so that it was not showing, again i set the limit to 30, and now the shipment name showing in order details page.
I faced this issue in my client website after downloaded into local and tried numerous way to solve the issue, there was no plugin to cause this issue, i completely disabled all the plugin and replaced new components files, BUT i did’t get any chance to make it work,
Finally i opened the configuration.php file which is located in the root directly of joomla, and found there was $live_site property under the JConfig class, i just emptied the value of $live_site variable. after this changes it worked successfully.
One day one of my clients contacted me with following error 406 Not Acceptable Error in Joomla while saving article, I tried many searches and found a clue in this forum http://forum.joomla.org/viewtopic.php?f=32&t=333553&view=previous , Yes the % symbol was problem in my client’s article content, there were in-line CSS width: 100%; line-height: 115%; etc.., then just replaced the % values with equivalent px values, the problem solved and the article saved without error message.
Some people say to disable the mod_security, but disabling this module would be high security risk to your web applications, Actually this module prevents the SQL injection codes and other malicious codes attacking your web site. It is better to ask your hosting support about the issue.
Here you can read more about mod_security