A follow-up to Reid's comment above: I have on occasion, put film in my Chromega drum but not processed it immediately. Even after a several-day interval, light leakage has never been a problem at all. I would not, however, deliberately leave a loaded drum in a sunny location for any extended period of time. I wonder if the Beseler drum light leakage could occur simply because the pouring spout is left facing upward toward any room light source(s); perhaps facing it downward would alleviate any problem.
That's exactly where it came from, but probably more from the light over my basement workbench rather than the window. In the future, if I load early, I'll place the drum on it's side and under a dark cloth. That should take care of it.