This error (and others like it) is raised when an old version of the Jalview Webstart JNLP is being used to launch the latest version of the application (for instance, because you have created your own JNLP file in order to increase the memory available to Jalview).
To fix, first make sure that you are using the latest version of the Jalview JNLP file (right-click or apple-click to save this link to a file) to launch jalview.
If you are using the latest version of the JNLP then you need to open the Java Web Start console panel, and flush any application caches and remove any old versions of Jalview listed in the application viewer. To do this:
- Locate and open the java console on your system (in your control panel or systems settings, but may also be in the Utilities section of the Applications folder on OSX.
If you have access to a terminal, you can usually open the console with
- Locate any jalview instances in your applications cache and remove them (usually, select the application and hit the delete or 'X' button)
Once you've cleared the cache, try to run the Jalview JNLP file again.