I've developed to being able to run small distances (a couple of miles) barefoot on a treadmill, which actually feels quite comfortable on the feet themselves.
Unfortunately, while this has meant I haven't had any lower back pain, I can't carry on with forefoot running because of the calf pain it is causing: no amount of stretching off before or after is getting rid of this.
More research on changing footstrike suggests midfoot running may be better, and certainly better than heel-striking.
The aim is to try and land with the foot relatively flat (mid- to forefoot) under one's centre of gravity, a slight bend in the knee, with a quick foot turnover, not overstriding.
Amazingly, the first time I tried this, the calf pain from forefoot striking was completely absent. The Achilles remain tight and sore though.
I'm still over two years away from MdS 2012 so it's worth trying out these different methods. I will at some point need to get used to running 20-plus miles at a time and remain injury-free. I know that won't happen if I go back to heel-striking.