I use encrypted USB disks for my personal backups. When I tried to mount a disk on a CentOS 6 host recently it failed. What had happened? It turned out that I had used the default options for cryptsetup and the defaults changed between the versions used in CentOS 5 and 6. To fix the problem I simply had to specify the old default values:
cryptsetup create -c aes-cbc-plain -s 256 -h ripemd160 usbbackup /dev/sdd
Perhaps it is better to avoid defaults anyway.