1- Go to the Windows Control Panel and click on Programs. Look for an entry for the Java program. Update to the lastest version of Java which is “Java 6 Update 26”. Once you update, make sure there is not more than one entry for Java (remove any old updates). *Google for Java to find free Java update (red button).
2- Install the Firefox browser, if you don’t already have it and take the test using Firefox.
3- Use a different computer and see if that works.
I was able to start the test using both IE 8 and Firefox 4, as a student. That points to some setting or software on the user’s PC as the problem. See possible solutions above.