Trying to backup files but says another backup operation is running

hi

 

my norton 360 premier is flagging up for a backup operation needs to be run. when i click for it to be fixed it says that "another backup operation is running". i have never had this problem before and am a bit confused to why it is happening. i have the norton premier edition 360 and windows vista is my operating system. not sure if i have given enough info but if someone can please help that would be great

 

thanks