4.5 Beta 4 (v4.50.0.1275) will be available for testing later this afternoon. Before installing please read Important Change post about the 4.5 beta.
To upgrade to Beta 4 when it ships, enter the *Update Now* command if you’ve switched to the beta channel before, or enter the *Set Update Channel to Beta* command if you're on a stable version (such as 4.3 SR-6). To install Beta 4 from scratch, see the notes and download link in this thread.
See Release Notes: http://wiki.logos.com/Logos_4.5_Beta_4.