Itunes 11.0.2 could not backup the iphone because an error occurred

I am using iTunes 11.0.2 with iphone 4s. Since March 8th, 2013, my iphone tries to backup to itunes and it keeps getting the error: "Itunes could not backup the iphone because an error occurred" I have tried everything on the troubleshooting website: http://support.apple.com/kb/TS2529 and nothing seems to work. My itunes works with my ipad 2 and ipod classic with syncing and backing up but not my iphone 4s. I even tried backing up on another computer and it still doesn't work. Please help.