For those updating to the newly released Mac operating system Mavericks (10.9), we already have several reports that Chimera crashes showing any molecule due to a graphics driver bug in the new Mac operating system. I suggest not updating to Mavericks immediately if you want Chimera to continue to work. Only Apple can fix this bug. But we will disable the advanced graphics that leads to the crash in tonight's daily build. So if you already updated to Mavericks you can try the Chimera daily build (available about 16 hours after this post) instead of the Chimera 1.8 release. If you want the Chimera 1.8 release to work in Mavericks you'll need to disable DrawElementsInstanced in the Chimera debug graphics driver dialog. http://www.cgl.ucsf.edu/chimera/docs/ContributedSoftware/debug/debug.html Disabling this graphics feature (which is what the daily build will do automatically) will cause rendering of large molecules to be slower when atoms are shown as spheres/balls or bonds are shown as cylinders, about 30 times slower. Still it should be as fast as the older Chimera 1.6 version where we did not use this advanced graphics feature at all. Tom