Any idea how to do this? The regular old Ctrl+Tab doesn't work on these.
I've tried SameTime 8.0 and 8.0.2, and Ctrl+Tab works to go between IM tabs (either vertical or horizontal).
For Notes, you can press Ctrl+F8. Look in the help under the topic "Working with window tabs", or "Switch window tabs"
You can also press Alt+W to get the window menu, then select the number of the desired window.
There are probably another dozen ways to do it... Like Ctrl+Shift+T, which brings up the thumbnails view of the tabs.
Use the Help, and Search for Keyboard Shortcuts for complete lists.