Over the course of the last two days, Apple has seeded two bug fixes for developers using OS X Mavericks Preview 3, which was first released on Monday. The first minor update, pushed yesterday, was aimed at updating the OS X Recovery function.
Today's small update resolves an issue that causes a Mac running Mavericks Developer 3 preview to reboot without warning. Both updates are available via the Mac App Store.
OS X Mavericks introduces a number of significant changes to the operating system, including a tabbed finder, full screen dual monitor capabilities, and Safari improvements. Mavericks is expected to be released in this fall after regular updates to the beta software.