"iTunes was unable to verify your device" after succesfully completing recovery mode on iPhone 4

I have an iPhone 4 which has never caused me any problems, until i updated to iOS7 it started lagging and battery didn't even last until midday (having it charged 100% in the morning!).

In just a few days it turned off automatically and wouldn't turn on. I googled and solved it by pushing the two buttons together for about 10 seconds. iPhone revived, and all the data was intact though many people states it would've been erased.

The morning after, using my iPhone more carefully not to have it crash again, it crashed. 10 seconds wouldn't do and I gave up, until the day after I found by surprise that the battery had run out and it finally showed some sign of not being completely dead!

I connected the cable to iTunes and pushed the Home button before connecting the iPhone and it entered Recovery mode. Recovery mode was completed and the iPhone had to restart to complete the process. While completing I get the error message "iTunes was unable to verify your device, please disconnect and reconnect your device". And from here I don't get anywhere, so I will probably visit Apple Store and ask what can be done, but if anyone has had the same problem please share any possible solution to this problem!