happy new years first of all,
to all y'all.

for the last few months i have been progressively advancing on the linear 5X5 (from madcows site), and have run in to a slight problem.
deadlifting on wednesdays causes by back to ache real bad (mostly on one side of my low back).
its important to state, that im using good form and keep my back arched, this has been verified by other trainers.
moreover, my grip is nowhere near failing, i dont feel the lift in my hamstrings or traps (used to but not nowdays).
im beginning to think that my lower back is a weak link, because it cant take any pressure.
obviously i cant keep progressing like this, im afraid ill injure myself, and the pains last a two to three days after each session.

any ideas what to do?
will i never be able to deadlift big?
do any of you guys expirience the same aches?