When Cubase opens ReWire it assigns audio channels to all ReWire channels regardless of whether they are used or not. A program like Reason that has 64 channels will use up quite a few of the available channels with the possible result that Cubase's channels may run out. To fix this we have created a file called 'REWIRE CUBASE FIX' and you'll find it in the folder named 'ReWire Cubase Problem' inside your Reason folder. If you move the file 'REWIRE CUBASE FIX' to the Extension folder (mac) or Reason folder (PC) you will limit the number of output channels to 16, leaving some space for Cubase's own channels. This problem will hopefully be fixed in coming versions of Cubase so that Cubase users can enjoy a full 64 channel ReWire.