Lower Back Pain with Dead's, but not Squats????

Question for anybody in the same boat previously. When I squat I have no problems with my lower back. Feels great, can rake my ass on the ground with decent weight and my quads and hamstrings swell up nicely. However, when I do deadlifts my lower back starts tightening up immediatly. Even doing a warmup of 60 Kilos with strict form it will start to tighten. And it hurts for days afterwards. Has anybody had this problem? If so what measures did you take? Thanks