Have you got firebug installed?! A non loading page would normally mean a JS error (missing file or function) so if you have firebug installed have a look at the error console to see if any errors exist.
Rootcause: I have checked LeftAndMain.php in cms folder, group js files will combine with base.js, cmsmain.js, leftandmain.js. but files are missing in appropriate folder(assets) then i checked chmod of assets folder 775 permission is set.
Resolved: i changed 777 permission to assets folder. now admin panel working fine