I tried a iPhone Backup Extractor software last night and had a problem using it. I emailed them and received this response today.
"From: Teodor Catalin (Support staff)
Hello Thingywingy,
Thank you for contacting us. We are sorry to hear that you are are experiencing issues recovering your restriction PIN.
The problem you are experiencing is a bug currently found in our latest version of the IPBE. The problem only happens for backups with IOS 6. Our development department has been made aware of this issue and is working on a fix for it.
Until then, you can easily reset your restriction PIN to 1234 using one of our previous versions. If you could kindly download the version for MAC or Windows, you should be able to solve your problem with version 4.7.4 in no time. Please note that with this version, you will have to restore to your device the backup in question, so kindly perform a fresh backup before starting this operation.
Once again, we are sorry for the inconvenience and we hope to have an update to this as soon as possible.
Regards,
Teodor"