I love Lower Body Blast! I just did that one on Monday.
I have always figured that Cathe uses a 25lb barbell, because I think her bar weighs 5lbs and she has two 10lb plates on the bar.
ETA: As for the other exercises where she uses dumbbells but doesn't specify the weight, I *think* she uses two 8lbs dumbbells for the walking lunges, one 15lb dumbbell for the leg presses, and two 8lb dumbbells for the hover squats. Am I forgetting anything? Ha!