If You install other ReWire compatible applications after You have installed Reason, these applications might overwrite the Rewire extension (the Rewire.dll if You are on a PC) with an older version, or even install a duplicate of the Rewire.dll in a incorrect location on the hard drive. Do a system wide search for "Rewire" and delete each and every instance of the Rewire extension or Rewire.dll that appears in the search result. Then insert the Reason 2.x Program CD, start an installation and select the Custom Install and make sure that You do not attempt to install the Sound Banks. This re-installation will only restore any missing files - like the Rewire files that You just deleted - and reinstall these.