unable to cannect AVRISPmkII with Atmel Studio

hello all we have a AVRISPmkII programmer and we successfully build led blink program in atmel studio version 6 after that when we try to download hex code from Tool-- Device programming we get following message

Unable to connect to tool AVRISPmkII (000200096781)

my question is which USB driver are install to atmel studio also where it available
or any other suggestion