I setup Win7/DebianTesting/Ubuntu 12.04 as triple boot, Debian and Ubuntu each on an encrypted volume (with separate root and swap partitions).
Installation order: Win7 --> Debian --> Ubuntu, Grub was installed on
/dev/sda, everything went fine, all 3 OS showing up in Grub UI and able to boot.
After an update with 12.04 (probably new kernel), Debian disappeared in Grub and so far I am only able to get Win/Debian or Win/Ubuntu showing up in Grub, according to these instructions:
blog post: restoring GRUB for an encrypted LVM
sda1 NTFS (100Mb)
sda2 NTFS (210Gb) Win7
sda3 extended partition where both Linux distros are installed into to LVMs:
sda5 boot (250Mb) for Debian
sda6 encrypted LVM (with separate Debian swap and root partitions)
sda7 boot (300Mb) for Ubuntu
sda8 encrypted LVM (with separate Ubuntu swap and root partitions)
with Ubuntu 12.04 liveCD I am able to decrypt and mount all partitions,
however neither Debian or Ubuntu boot partitions are recognized/useable to use chroot and to reinstall GRUB into