lost all my contacts & sms after downgrade

I downgraded my phone from ios 4.1 to 4.0 to be able to unlock it; however, now i lost all of my contacts and text msgs; whenever i try to retrieve from back up on itunes i get an error message " itunes could not restore the iphone because the back up was corrupt or not compatible with the iphone is being restored"

I followed some other website which said that I should go to the back up file and change the version number from 4.1 to 4.0 so itunes can read it after i did that itunes read my iphone but cant restore

Can someone please help!!!!

I believe you would have needed to save your shsh blobs on your own or through Cydia while RUNNING 4.0.1 originally (before you went to 4.1)in order to downgrade to 4.0.1 from either 4.0.2 or 4.1.

If you have a backup in 4.1, your best bet would be to stay on 4.1 and wait for a hopefully/eventually released unlock.