EDIT** pfff too late
Download and install an older OS, say .64 from TMO. Run DM (desktop manager) and I believe it will ask if you want to downgrade, click yes and go for it.
Or can get um that tool... that wipes the OS from the BB and then reload the .67 OS once you've restored the blackberry.alx with the one from jibi's thread that already has the themes unlocked.