I am using Fedora Core 14 and have installed Selenium Module for PHP. I was not able to run PHPUnit tests on Yii Framework. I tried running Selenium server 1.0.1 and upgrade to 1.0.3 solved the problem.
I downloaded the Selenium Remote Control from here and extract the file selenium-server.jar, renamed it to selenium-server-1.0.1.jar and placed it in /home/myusername/.netbeans/6.9/modules/ext/selenium overwriting the old jar. Then I restarted Netbeans. Now, testing works.
Hope this helps.