This happens frequently enough that I came here looking to see if others were experiencing the same, but I didn’t see any on the first couple pages or find any in the search. That said, let me explain.
I set Ctrl+Z to be my action cam macro, then I set that macro for Mouse 3 because I plan to switch between views regularly. It works most of the time as should be expected, but once in a while, the UI, including bags, menus, dialog, reticle, skill bar, party, everything, just vanishes. On one ocasion, I got it to come back by hitting the ctrl+z macro a few time, but never again. My skills still work, and I can still pick up stuff, but dialog interaction is impossible and I can’t see my gear or other windows when this happens.