Case close on click of Resolve button programmatically

Hi,

I am trying to close the case  programmatically when i click Resolve button on case entity .  I am  triggering a plugin which fires on close message  and in the code there is no error and it's working fine . But when i try to open the  case i found that status is  still active and when i try to close case again  after clicking on resolve button i am getting error as in the below

screen shot. I am using this example in the url to close the case

http://mileyja.blogspot.in/2011/08/close-case-using-jscript-or-net-in.html

 .

Abhishek