The page that you display in the Edit Panel, does it use the same masterpage as the EPiServer pages displayed in the panel? By doing that you make sure the scripts are loaded. The GUI probably breaks because your plugin does not load these scripts. Take a look at this blog post for some tips on using the system masterpage and some other tips: http://world.episerver.com/Blogs/Dan-Matthews/Dates/2010/3/A-few-tips-on-UI-Plugins-in-CMS6/

I think  you are right, Yes i am using diffrent masterpage i.e

this.MasterPageFile = ResolveUrlFromUI("MasterPages/EPiServerUI.master")

bcoz i want that page look like admin scheduledplugin.

How i can achieve this?

Well, what you want is to mimic what scripts that are loaded in "working" edit panels. So just look at the rendered code from them and make sure your page loads the same scripts. If nothing else works you should basically be able to copy the script paths and hard-code them into your page. Not elegant, but you could start with that and then refine your solution.

Thanks for support.I found simple solution for this.We have to write these two functions in page and its working fine :)

function onNavigate(newPageLink)
  {
   return -1;
  }
  function onCommand(newCommand)
  {
   return -1;
  }