Glad you found the problem.
A roll of rubylith is good to have on hand for the darkroom. I don't know what I'd do without it, aside from completely boarding up my basement. I hang flaps of it over the edges of my sliding door, and a sheet of it over my basement window. Instead of blocking the light, it turns it into a safelight, and it is easily reversible. I get mine at a screen printing shop.