I believe you can submit it anyway cause the final submission page includes a section for monitoring the status of supporting info, i.e. recommendations, gre and toefl scores, etc. it even includes a section where you can add recommenders (i guess in case someone doesn't come through). so, i think it's safe to assume that you can submit it and continue to tweek reco info.
nothing more annoying than pestering a recommender. gah.