The steps I used are as follows, in brief:
1) Installed Vista first (actually pre-installed on laptop)

2) Installed Ubuntu second using encrypted physical volume with LVM inside it and 2 partions / and swap inside the LVM(at this point, grub was in the MBR)

3) Ran full windows system encryption (not full disk encryption) through TrueCrypt and let it write its bootloader to the MBR. (obviously overwriting Grub in the MBR)

4) Booted with a live cd and copied the truecrypt bootloader from the MBR to a file in the /boot partition (sda2)
use these commands to do so:
dd if=/dev/sda of=/mnt/boot/truecrypt.mbr count=1 bs=512
dd if=/dev/sda of=/mnt/boot/truecrypt.backup count=8 bs=32256

5)Reinstalled grub to the MBR using these commands:
sudo grub
install (hd0,1)/grub/stage1 (hd0) (hd0,1)/grub/stage2 0×8000 p

6) Added a chainloader to the menu.lst Vista entry to point to the truecrypt bootloader within the /boot partition like so:

title Windows Vista/Longhorn
rootnoverify (hd0,0)
makeactive
chainloader (hd0,1)/truecrypt.mbr
boot

The only partition not encrypted in the /boot partition so far, which is fine. After grub loads, no matter which OS I choose, I enter a passphrase and that OS starts.

For more detailed instructions which I pulled from but which are for XP instead of Vista, use this link:

http://ubuntuforums.org/showthread.php?t=761530