low DNA yield after extraction - (Jul/17/2009 )

I'm using Qiagen's DNeasy blood & tissue kit, to genotype mice. I use about 0.5 to 1 cm of the tail tip from 4 to 5 week old mice. I've had great PCR results with this DNA for some reactions, but always had trouble with one particular reaction. After DNA spec (using a NanoDrop) I discovered my DNA concentration is only 10 to 17 ng/ul. I spec'd some old DNA (before I worked here) and they had 20-27 ng/ul up to 50 ng/ul.
I follow the instructions to the letter for the kit. I warm the buffer ATL to dissolve precipitate, premix buffer AL w/ 100% ethanol, and I elute in one step using 200 ul of buffer AE.
Should I warm the buffer AE, or elute in 2 steps of 100 ul each? Should I spin down the tubes after digestion w/ proteinase K to remove hair? Nobody else has had to do this and they have good results.
Are there any other suggestions as to what I might be doing wrong?
Thank you so much for your help.

If you are really suspecting5 the kit you have to first clear t6at point. For that i can suggest to take Known concentration of DNA and use the same kit and isolated the DNA and see how recovery you get.if percentage of recovery is less t6an 70% then there is problem in kit solution.