If you've gotten this picture Untitled.png below,
then that means when you changed a part in your code, you didn't exit the opened window first.
Open up task manager and go to processes.
Find java.exe and delete it.
Rerun your sketch
Hmm. OK
Thats a solution that has worked for me. Im just wodnering if it will work for you. Please reply to confirm or adjust.
I've never had to do it with the arduino IDE but it's worked for me, in the past, with other applications that tie up the com port.
Thanks for the reply.