Cover Flow previews blurry, how to force a system-wide re-draw??

Did an archive and install from Tiger, and now cover flow previews are low-res and blurry, presumably from the thumbnails in Tiger. Question is, how can I tell Leopard to redraw the thumbnails from scratch?? Anyone know?

EDIT: Yes, I can force a redraw ONE-BY-ONE by opening Info and deleting the icon, so how can I automate this?

before:


after:


K, how to automate this??

Thanks for the move.

I think I figured it out: a program like CocoThumbX can remove thumbnails from batches of files. Works like a charm as far as I can tell