Someone mentioned that I needed to "save my current cui file." Whut? How do I do that?
I think they used wrong terminology, and were telling you to "save your current Workspace". When you make any change to your workspace, such as add/remove/move a toolbar or tool palette, make sure you save the changes to your workspace. Easiest way is using the Workspace toolbar - click on it, do "Save current as", then find your current workspace in the dropdown list and overwrite it.
You can also configure this thing to "autosave" any changes you make to your workspace, but personally I don't like that option.
More workspace info:
Workspaces define the layout of toolbars, menus, etc. on the screen. They reside in your Main and/or Enterprise CUIs, and you can have more than one Workspace in each CUI. Workspaces in the Enterprise CUI are read-only. Workspaces in Partial CUIs are not visible, and must be transfered into either your Main or Enterprise CUI if you want to use them.
Autodesk seems to think we should use Workspaces to define "task oriented" layouts of toolbars and menus, but I find that annoying. It takes too long to switch workspaces, and I always find myself needing a toolbar or menu that is in another workspace. Instead, I use a single workspace all the time, which has all the tools I regularly use easily-accessible. I then use one workspace for each monitor setup I use. For example, I have one workspace setup for my single 20" monitor at work, but I have another workspace setup for my 20" + 17" dual-monitor setup at home. I generally never change my active workspace while I'm working.