Problem restoring backup of iPhone on iTunes after updating to ios7, there is no error code either

Hi, I have an iphone4.

I created a backup, and updated the iphone to ios7 after getting messages from apps saying they need 4.3 ios or higher.

Now I have an iphone 4 with ios7, but no contacts, photos, messages, anything. It is like a new phone.

I read that this would happen and it was normal, hence I have the backup.

So in itunes, the iphone4 has 3 sections: iphone 4, backups, options

I went to the section "backups" > this computer > restore backup

A small box opens up for me to select the backup. Then I clicked "restore".

"Restoring iphone from backup" runs, the time it finishes is around 10 minutes.

When it finishes, an error message always pops up saying "itunes could not restore the iphone from backup because an error occurred".

There is no error code. I've tried restarting both the iphone and computer.

I don't know what else to do. Please help!