CB 1.65 bug

It has been nearly 3 months since I released CheckerBoard 1.65, and I hate to admit that I got bug reports nearly instantly after its release. I finally took the time to look into them (partly because my girlfriend is in Spitzbergen). I cleaned up a lot of my source code in CB 1.65 with the goal of making it public with this release, and unfortunately, I managed to add a rather serious synchronization bug to it. I believe to have found it, some final testing is still required, but probably there will soon be an update available.