From time to time you may experience problems with the execution of the Java plugin in the Opera browser. This happens because its path is not correctly configured in the options.
To resolve the issue, open an Opera browser window and enter
into the URL bar. There should already be one path in the Plugin Path line. Enter a semicolon and add an additional path to the line. On a default Windows 7 and 8 installation, the Java plugin path should be
depending on your version of Java. Afterwards, scroll all the way down and save. Restart the browser the the issues should be solved.