The backups are stored as packages. If you select the back up and go to "file" under the Finder menu, you should be able to pick "show package contents." It won't be a clean restore, but all your files are still in there.
I think these back up issues are actually common with the Leopard upgrade. I would suggest keeping the back ups intact and safe in anticipation of a Leopard and/or back up update. You can manually copy out any files you want now or all if it.
Also, and not sure on this off the top of my head, but I think if you copy the back up file to your desktop and double click it, it may show up like a mounted drive and give you access to the files it contains.
Good luck.
. Anyone?
