Update: I've found and fixed this. The fix will appear in the next release, b13. (I know that many of you would like me to instantly release a fixed version, but I still have other, very serious crashing bugs to investigate. I would like to get those solved for the next release as well. Please be patient while I work on this.)
Crashes and Freezes
Many of you are also discovering and reporting a bug that I did already know about, and which is called out in the b12 Read Me file, in recent blog posts here, and on the Bug List page: Crashes can occur when you use Undo, Redo, or Deal (clicking on the deck). On my systems this happens rarely, but it does happen. On some of your systems it clearly happens quite easily.
Please don't send me any more bug reports about this. I usually don't ask that, but I am getting so many that I don't have time to work on the problem: all my time is going to answering the reports.