Just spotted that Adobe have released an update to the Flex 2.0.1 SDK, over at http://www.adobe.com/go/kb401224.

And knock me down with a very small feather if they've not fixed the reappearing data grid columns bug I checked a work around for into our SVN for this very morning :-)

Seamless, easy install (unzip over the existing SDK), recompile and your off.