[djsanta]

I've had the same problem before.  Crush was the first culprit.  I run a two-vessel system and after a traditional mash I do a full volume, continuously recirculating sparge and recirc until I hit my numbers.  With a bad crush I've had that take as long a 3.5 hours!  Double crushing at the LHBS is the easiest fix.

I also discovered that my thermometer was off, so when I thought I was mashing at 152F I was really over 160F.  I switched to a digital thermometer and haven't had any problems since.

[cornershot]

I use an old Valley mill. The gap is indexed and not infinitely adjustable. The smallest gap gets me the best crush but if I try it on the first pass the free-spinning roller stalls and it's a pain to get it restarted. So I need to double crush. First pass on the wideer gap and second on the tightest gap. The result is a beautiful crush with the endosperm crushed to fine grits and the husk is almost left whole.
As far as efficiency goes, if I go by Kai's first runnings chart in his understanding efficiency article my conversion efficiency is usually near or at 100%. After lautering and trub loss I'm down around 75% brewhouse efficiency.