I first posted about broken vhd - avhd chains in December 2009, And since then I have helped many people throughout the world in recovering their data and made some friends along the way.
I have recovered data for people in france, germany , uk, australia, usa, brazil
A guy called Dave Loughner from Innovative Solutions in New York pointed out a great utility for recovering data from avhd & vhds.
It is Disk Digger and only cost $14.99, Best money you will ever spend if your really stuck. Dave tried about 30 recovery products before coming across Disk Digger.
As of writing this www.diskdigger.org is down but you can download it here
Also a point to note. The disk digger solution is absolutely the last resort as nothing is as good as merging all avhds and having a healthy server at the end.Using disk digger will get you back up to 50% of your data but not all.