Look at the top of the screen (title bar).
RB has to generate all the tracks before it will be responsive.
Maybe this is taking longer on your machines (?)
That title bar should show the progress.
RB is not like BiaB in that it generates as it plays, instead RB generates first thing.
Thanks for you response.
I created a test.sgu consisting of two bars with no loop.
When I loaded that file RB went into instant endless lockup with 98-99% CPU usage.
It's interesting that a yellow box very briefly flashed in the upper right screen too rapidly for me to see what it said....