Have you tried drop sets ? They worked for me better than anything. You might also want to ease up on your back work since the biceps are involved in those movements as well.
Im doing this right now,.. once a week (sunday). I must say, that normally, I would have to pound my bicepts for what seems like 45min,.. in the end, I have to get a certin number of reps in to really work them.
I suggest doing drop sets.
Do a few warm ups, and then run the rack. Take the weight you can get 5 of, alternate curls, then go down 5 pounds. keep going down (even if you can only know out like 3 reps at a particular weight- No more then 10 seconds if you have to between sets).
Burnout id GREAT for it's shock value!!!
I like running the rack twich. Sometimes I have to drop dfown in 10lb increments depending...
After which (well, for the time being) I grab the 35's and take a seat (incline) and pump out double sets. (do one set of eight reps, put down the weight, rest for 10-15 seconds, and do another set.
About 2-3 double sets and beleive me, after everything, your bicepts will be trashed!
-MAke sure you dont have anything you'll need those arms for the next day.
I like to do them Sunday, becasue I do squats on Mon, and bench/Tricepts tuesday.
Do this ONCE a week.