Atlassian just broke Sourcetree Mac and Windows with 2 updates
twitter.com
twitter.com
http://downloads.atlassian.com/software/sourcetree/SourceTre...
https://downloads.atlassian.com/software/sourcetree/windows/...
(Disclaimer; I'm Atlassian employee, although not on Sourcetree so I don't have any special insight.)
The team now acknowledged the problems on Twitter and is said to be working on fixes: https://twitter.com/sourcetree/status/699624992003244033
("Funny" that this is the first public mention of @sourctree of any update - nothing on the blog, Twitter feed...)