This problem is due to a known bug with EPiServer Manager 1.3.1. There should be a newer version of EPiServer Manager available (1.3.2 at least).
Thanks for your reply..one more doubt.My colleagues installed the EpiServer Manager 1.3.1 version only.They didn't get any problem,but i got problem with the version.If it is a bug,everone should face the problem..isn't it?
Its a bug, "0045529: The manager throws an excpetion if installed under an existing site and not supplying a virtual directory".
The workaround was to let the Manager create the site (right click on "local computer") or install in a virtual directory. But this issue has been fixed in EPiServer Manager Verson 1.3.2. And 1.3.3. is the latest version so go to meny "help" ->"check for update" to update.