Message: not enough computer space for iphone backup My iPhone 4s won't backup. I receive the message: 


  not enough space on computer.


There is plenty of space on my mac, 220 gigabytes free.
I had this issue. It finally came down to backup software - in my case CrashPlan. I "slept" the backup for a few hours, restarted the backup, and it completed successfully. It seemed like CrashPlan would lock the file after the iTunes finished writing the file out right as it was renaming it from a temporary name to the permanent name.