14:45:33.140 WARN - Failed to start: SocketListener0@0.0.0.0:4444
Exception in thread "main" java.net.BindException: 
Selenium is already running on port 4444. Or some other service is.
at org.openqa.selenium.server.SeleniumServer.start(SeleniumServer.java:378)

at org.openqaselenium.server.SeleniumServer.boot(SeleniumServer.java:224)
at org.openqa.selenium.server.SeleniumServer.main(SeleniumServer.java:188)

This is the most common error which is encountered while starting the selenium server. The origin of this error is the fact that selenium server always tries to listen at port 4444 by default .

There are chances that when you are running tests, the server might not be shutdown properly. In this case, when you try to re-run your tests, you may encounter the following error

I Google for a solution and finally i got solution from my friends blog

Solution for the above problem is , type the below in the browser URL and the server will be stopped

http://localhost:4444/selenium-server/driver/?cmd=shutDownSeleniumServer

Now your should be able to see the message "OKOK" in the browser window. Your server now shut downed. 

Now run your script from eclipse....server will start now with out any problem

Hi...

Here i want to mention about the problem i faced with Firefox(3.6.*)..I created some test scripts using JUnit and able to run in FF(3.5*). Later i upgraded my FF version to 3.6*..Then i got problem

"Could not start Selenium session: Failed to start new browser session: Unable to delete file C:\WINDOWS\TEMP\customProfileDir1249f05ea902412fa46b6c703435ffe6\parent.lock"


I posted question in Google selenium forums...some friends gave suggestions to delete lock file..etc..But it didn't work.

One day i am searching for the same bug in Google..suddenly i found the answer for that...

Here is how to solve that problem