Importing videos into CERTAIN projects

Hey all,
I’m using latest versions of everything on Mac (irrelevant here)…
My problem is that I CAN import a certain video file into a certain project A (using File/Import). No problem. No sweat. Now if I open another project B and try to import THE SAME VIDEO FILE, Cubase doesn’t do anything (it accepts the command but nothing happens). I tried many things, relaunching Cubase, etc and I always get the same result: I can import the video file into Project A, but not into project B. I’m curious to know if anyone has seen this problem before.