Highlight the folder in question, file --> Get Info --> Sharing & Permissions --> Unlock --> Set permissions to give you ownership --> Click on Gear, select Apply to Enclosed items.
Sorry, misread the question.... It's a permissions issue, but what your really asking is how to merge two different Time Machine Backup stores.
You really can't merge them... Time Machine considers each install to be a different machine, which is why your running into an issue. For example, your first install isn't snow leopard... So why would you want your Snow Leopard OS files to be equated with your non-Snow Leopard files...? At least that's part of the reason that Apple has designed it this way...
I think I know what has happened, but I'm not sure the best way to resolve it.
You originally had a single partition, which contained leopard, and your user account? You then shrunk the Leopard partition, and made a second partition for Snow Leopard? Installed Snow leopard, and then restored from backup with the target being Snow Leopard's partition?
Did you do a User Migration with restore? Or a Snow Leopard install with Time Machine restore? I suspect a SL Install w/restore...
I suspect that the user account in Leopard is a different user ID than your SL user account (eg 501 vs 503). Can you check? System Preferences --> Accounts -> Right Click on Account --> Advanced -> What is the User ID on Snow Leopard? And on Leopard?
That would explain your permissions issue. If you haven't done much in Snow Leopard, I would suggest creating a temporary Admin account, deleting your current user, and then using the User Migration tool to bring your old user account over from the Leopard partition... Seamless, and should do exactly what you want...
I know you can do it manually, but since your user account already exists, I don't know what impact it would have in manually correcting the user id, etc, in Snow Leopard...