I have the same issue. It's ridiculous that Apple doesn't provide a conversion tool. Yes, they keep 09 when you upgrade. No, they don't give you 09 when you buy a new MBP, install keynote and need to open an old file. Am I supposed to drag a copy of 09 with me everywhere I go in case I need an old file?
So, this isn't the best solution, not even close, but you can open Keynote 09 files with Preview. You lose all the animations and transitions (and if you have lots of hidding and showing, you might not see everything) but you can at least export all the slides as PNGs from preview and have access to the content.
Like I said, not ideal, but better than not being able to see anything.