Beth L. / Putz### (love the screen name even if I can't remember all of it), I'll poke out a quasi-revolutionary suggestion:
Cathe at times in her rotations on the Rotation forum will schedule a non-Cathe style workout: a run, a walk, do-it-yourself ab work, etc. It may be time for you to let go of the DVD-based weightlifting routines and cook up one of your own to do for awhile, where you can go at your appropriate rep speed while lifting the heaviest weights you can. It could be that what's limiting your ability to add weight load and strength to specific muscle groups is that you're attempting to hit all of the reps in your DVDs, and the rep velocity might not lend itself to pure strength building.
Although I always buy Cathe's weight lifting DVDs to get ideas for how I can incorporate new lifts into my own set, I never follow a weight lifting DVD as produced. (Sorry, Cathe; hopefully my consumer dollars will make up for that!) Having developed and followed my own program over the years, I can now do dumbbell overhead presses with 26.25-lb (EACH) dumbbells, and in fact will be upping the weight load to 27.50-lb (EACH) dumbbells next Sunday. I could never lift that heavy if I weren't on my own rep timetable. The weight load increases have always been very small and incremental but sustained, and the strength slowly but surely build from there, not only for the working muscles but also for the supporting muscles like those in the hands, forearms and core.
Just a thought.
A-Jock