Bro abhinav3 ,first check your phone free memory, it must be upto 5 mb space avilable at there, then check configration settings if you use idea network then set it on ideainternet/idea gprs .second thing is you have working dataplan avilable to download update. some times weak network connection of service provider is the reason that don't download update,then you have to go in good network area.
you also check your nokia express browser is work well or not. if it work well you definatly download update