Can't install 32 bit libboost on 64 bit system

[Dan Kegel]

On precise alpha1, fully updated, I'm trying to do both 32 and 64 bit builds of a c++ app that uses boost. Here's my test script:

sudo apt-get install gcc g++ libboost-dev libboost-date-time-dev
g++ -m64 mymain.cpp -lboost_date_time -o mymain64
sudo apt-get install gcc-multilib g++-multilib ia32-libs libboost-dev:i386 libboost-date-time-dev:i386
g++ -m32 mymain.cpp -lboost_date_time -o mymain32

The 64 bit binary is built ok and runs fine, but the 32 bit versions of boost don't install; apt-get complains
 libboost-date-time-dev:i386 : Depends: libboost-date-time1.46-dev:i386 but it is not going to be installed
 libboost-dev:i386 : Depends: libboost1.46-dev:i386 but it is not going to be installed

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: libboost-dev 1.48.0.2
ProcVersionSignature: Ubuntu 3.2.0-9.16-generic 3.2.1
Uname: Linux 3.2.0-9-generic x86_64
NonfreeKernelModules: nvidia
ApportVersion: 1.91-0ubuntu1
Architecture: amd64
Date: Wed Jan 18 14:12:39 2012
InstallationMedia: Ubuntu 12.04 LTS "Precise Pangolin" - Alpha amd64 (20111130.1)
ProcEnviron:
 PATH=(custom, user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: boost-defaults
UpgradeStatus: Upgraded to precise on 2012-01-18 (0 days ago)

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.