I updated to LR 4.3, ACR 7.3, and CS6 11.0.3 yesterday even though I'm not on a Retina MBP.
Anyway, last night I was doing some edits. Opened LR catalog, edited a RAW in PS, saved the PSD which kicked back to LR. Did some final touch up using the Soften Skin adjustment tool and when I clicked on an area of the photo to make the brush stroke, LR would crash. It did it several times in a row and I finally got it to stop by clicking on the brush tool, clicking done, then reclicking the brush tool. I'm not sure if there's some kind of UI bug or what not, but that's really annoying. I have LR automatically sending bug reports on crashes.
It helps if you clear the history when you work with the AdjBrush or the Clone Tool.
In the header of the History panel, to the right of the word <History> there is a small < X >. Click on it, this will clear the history.
But be aware, the cleared history steps cannot be made visible again in the history panel.
Clearing the history will not undo the develop steps, your photo does not revert back to original. But you can't see the steps any more in the panel.
upgrading Mac OS is not the absolute best advice. I have a very well managed system and refuse to upgrade from 10.6.8 because it could change things in a way that I would like find unsatisfactory. The newest OS -- either Windows or Mac -- isn't always the best. Besides, LR is supposed to be compatible with 10.6.8.
What are you doing before it crashes Rusty? Just brush work? Or is it happening elsewhere? And what system specs?
If you don't want to update your OS from Snow Leopard, try rolling back to 4.2 for now. There are a couple of other brush bugs in 4.3, so try 4.4 once it's released.
Since an OS update is what's fixing the problem, it sounds like a conflict with something in the OS - perhaps a driver issue. If you want to do a little troubleshooting on 4.3, resetting preferences is worth a shot. http://members.lightroomqueen.com/index.php?/Knowledgebase/Article/Vie w/1148/198/how-do-i-delete-the-lightroom-preferences-file
Thanks for your help Victoria. I actually have not had an issue since the first week. It happened with a very specific folder and was random, not just using brush strokes. It would happen even switching to another image. But LR seems to have settled down for now. So I'm not going backward and reinstalling 4.2.