Comment 6 for bug 824346

Nearly worked for me :

alex@Leon:~$ sudo apt-get install libgl1-mesa-glx:i386 libgl1-mesa-dri:i386
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following extra packages will be installed:
  gcc-4.5-base:i386 libc6:i386 libdrm-intel1:i386 libdrm-nouveau1a:i386
  libdrm-radeon1:i386 libdrm2:i386 libexpat1:i386 libffi6:i386 libgcc1:i386
  libglapi-mesa:i386 libllvm2.9:i386 libpciaccess0:i386 libstdc++6:i386
  libx11-6:i386 libxau6:i386 libxcb1:i386 libxdamage1:i386 libxdmcp6:i386
  libxext6:i386 libxfixes3:i386 libxxf86vm1:i386 zlib1g:i386
Suggested packages:
  glibc-doc:i386 locales:i386 libglide3:i386 pciutils:i386
The following NEW packages will be installed:
  gcc-4.5-base:i386 libc6:i386 libdrm-intel1:i386 libdrm-nouveau1a:i386
  libdrm-radeon1:i386 libdrm2:i386 libexpat1:i386 libffi6:i386 libgcc1:i386
  libgl1-mesa-dri:i386 libgl1-mesa-glx:i386 libglapi-mesa:i386 libllvm2.9:i386
  libpciaccess0:i386 libstdc++6:i386 libx11-6:i386 libxau6:i386 libxcb1:i386
  libxdamage1:i386 libxdmcp6:i386 libxext6:i386 libxfixes3:i386
  libxxf86vm1:i386 zlib1g:i386
0 upgraded, 24 newly installed, 0 to remove and 1 not upgraded.
Need to get 0 B/14.6 MB of archives.
After this operation, 44.3 MB of additional disk space will be used.
Do you want to continue [Y/n]? y
E: Internal Error, Could not early remove libgl1-mesa-glx

I read multi-arch was only (and properly) handled from Oneiric (which will be released soon).

Anyway, thanks for the tip, it sounds promising.