Can't restore OS3.x backup to iPhone running OS4.x

[shalom.]

I backed up all my photos, contacts emails etc while on OS3.x, then managed to wipe and upgrade to OS4.x. Now when I try to restore from backup I can't because it's a backup from OS3 and so I can't restore to OS4. It appears that you can't downgrade from OS4.x to OS3.x unless you have saved the SHSH blobs from the iPhone before the upgrade. So I now have a great iPhone 3GS running this great OS4.x software but can't get my media/data back from backup. Please help there must be a way around this issue. Thanks for any advise.
Chris.

[i.Annie]

That's expected. The back up was on a firmware too old to be supported by iOS 4. There's a thread somewhere on here that says something about how to force the back up, but it seems more unsuccessful than not.

You might try downgrading, load the back up, extract any data you need via SSH with a data extractor.