Where did you load the film into the tank? I had something similar happen when I used to load 220 film in a darkened hallway. It looked dark, but wasn't, you would still get some stray light comming in even if you stuffed blankets under the doors.
Also, is the floor of where ever you are loading the tank carpeted? With 220 film I would occasionally get some static electricity "glow" for lack of a better term on the film surface while unrolling the film to put on the reel.
Those are just some thoughts.