I also toggled off the check mark in front of "UI" under the Advanced > Rendering Features > UI tab. While that removed everything immeditely, there was no way to get the UI back, using CTRL+Shift+U, CTRL+Alt+F1 or CTRL+Alt+Fn+F1. Couldn't even exit the program, only option was to bring up the task manager and force program closure. My operating system is Windows 7 Professional, 64-bit install, nothing different than before install of latest edition of Official SL Viewer.