iOS7 update saying not enough free space on computer to backup iPhone???

I keep trying to update to iOS7 and when my macbook extracts data and goes to backup it keeps saying I dont have enough free space on my computer. I have literally deleted EVERYTHING. My HD says I have 54Gig of free space available. Deleted my last iphone backup. Everything is up to date software wise. Restarted Computer and all. I have about 30Gig on iphone 5. I just dont get it. simply deleting my last iphone backup should have given me enough free space to do new backup/update. Frustrating.