Hi, this might be a problem with ur cable or the dock. I recommend trying another cable on another computer and see if it works. If this does not work, then ur memory or some part related to the transfer of information inside the phone or relating to the phone might be damaged or corrupt. I know this will not make any sense but try it out. Write back with what happened. Good luck.

srikanthnaru, just like John Savio suggest, besides check your cable, your dock connector as well as using a different computer, check with Apple on that one as well "These errors typically occur when security software interferes with the restore and update process. Follow Troubleshooting security software issues to resolve this issue. In rare cases, these errors may be a hardware issue." So I would this first. Error 23 can also be caused by a bad battery.