When backing up iPhone 5 to iTunes get message not enough space on computer

Question

On backing up iPhone 5 to iTunes keep getting message "iTunes could not back up "M iPhone" because not enough space on this computer."
There is actaully 125 Gb free on computer. Have run repair disk permissions through Disk Utility
Any suggestions please?
Thank you

Answer 1

Problems such as yours are sometimes caused by files that should belong to you but are locked or have wrong permissions. This procedure will check for such files. It makes no changes and therefore will not, in itself, solve your problem.
First, empty the Trash.
Triple-click the line below to select it, then copy the selected text to the Clipboard (command-C):
find ~ $TMPDIR.. \( -flags +sappnd,schg,uappnd,uchg -o ! -user $UID -o ! -perm -600 -o -acl \) 2> /dev/null | wc -l
Launch the Terminal application in any of the following ways:
☞ Enter the first few letters of its name into a Spotlight search. Select it in the results (it should be at the top.)
☞ In the Finder, select Go ▹ Utilities from the menu bar, or press the key combination shift-command-U. The application is in the folder that opens.
☞ Open LaunchPad. Click Utilities, then Terminal in the icon grid.
Paste into the Terminal window (command-V). The command may take a noticeable amount of time to run. Wait for a new line ending in a dollar sign (“$”) to appear.
The output of this command, on a line directly below what you entered, will be a number such as "41." Please post it in a reply.