Are you able to recover with all that back work or better yet, are you really working enough on your deadlift in order to improve it?
If your stuck in a halfway position, either just above or below the knee, I would suggest really low box squats, romanian deads or good mornings as an accessory. It's tough when you max on a dead or go up to a triple max because it's very taxxing on the CNS and when you miss a dead, it's very defeating mentally, there's no excuse other than you didn't hit it. Now you can blame it on form but you can't correct something you can't see, only someone else who know's what their doing can help you in that department.
Go here...
http://www.westside-barbell.com/articles.htm, there is a three part series on the deadlift and in the 03 block there's a bunch of info regarding plateaus as well...
On a side not straight from the horses mouth, guys at westside have started using foam pads on their boxes and lowering the box height when they squat. They sell these at elitefts.com but also you could use the ones they have lying around the gym. While these guys have for years box squatted on a solid surface, some well above and well below parallel, this has started to really strenthen their hips, that instability has actually increased hip strength and their ability to stay tight, just a thought....