Comment 3 for bug 363771

aes-x86_64 is not the only module which is missing, there are many more crypto modules missing like:
xts, md4, ...., which is really anoying, because I can't mount my xts encrypted partitions.
In the filelist of the kernel image are all modules listed: http://packages.ubuntu.com/lucid/amd64/linux-image-2.6.32-21-generic/filelist

On the lucid amd64 alternate there are only:

aes_generic.ko
arc4.ko
ascyn_tx [dir]
blowfish.ko
crc32c.ko
serpent.ko
sha256_generic.ko
twofish.ko
twofish_common.ko
xor.ko

in the crpto dir (/lib/modules/2.6.32-21-generic/kernel/crypto/)