Sorry, I really can't reproduce the problem here, though I'm using 2.6.22-grml. 
Can you please try upgrading the cryptsetup package and if that does not work 
yet try using linux-image-2.6.22-grml (available from grml-testing repository)?

% dpkg --list cryptsetup linux-image-2.6.22-grml
[...]
ii  cryptsetup                2:1.0.4+svn29-1+b1        configures encrypted 
block devices
ii  linux-image-2.6.22-grml   grml.01                   Linux kernel binary 
image for version 2.6.22-grml