When i upgraded to lion my computer froze during a time machine backup. So i turned it of and it cause a file to be made called an in progress file my sparse bundle. Since then i have never be able to successfully back up to my time machine. I was told to delete the in progress file so i have dragged it into trash but it always freezes two thirds through the deletion at the start it says the some of the files are locked are you sure you want to delete. After clicking yes it goes fairly swiftly until about two thirds of the way through as i said and then my whole computer tends to freeze without any other applications running. I can not even move the in progress file back in to time machine either. Any ideas on what i should try next?