My Ipad 3 wifi failed while upgrading to IOS 7 over wifi. unknown error occurred (27)

My Ipad 3 wifi failed while upgrading to IOS 7 over wifi. I think that the reason was that upgrade was being performed while moving around the building and probably, the Ipad could not roam in between Access points. The building has very strong signal provided by a lot of CISCO controller based Access Points.

The Ipad when powered shows the USB picture to be connected to Itunes. The itunes finds it and starts restoring to 6.0 versions.

Restoring ipad software bar on itunes compleates

verifying ipad software compleates

but fails verifying ipad restore on error message The ipad "iPad" could not be retsored. An unknown error occurred (27)

The status bar on the IPad device (under the logo) stops on about 85%

Itunes is latest 11.1.3 and firewall my pc is off, antivirus off

Any idea how to restore it? I don’t think that there is a HW issue because the Ipad was workin. The restore almost compleates but why verifying restore fails?

There are no information on error 27 anywhere