I found a workaround on this site:
http://askubuntu.com/questions/93571/cannot-install-ia32-libs-on-a-64
-bit-ubuntu-installation
Create this file:
sudo nano /etc/apt/preferences
and insert the following lines:
Package: *
Pin: release a=quantal*
Pin-Priority: 2012
Ctrl-X to quit and Y
This error indicates that you had unofficial library packages installed
from a (probably no-longer-configured) ppa. Allowing the system to
downgrade these library packages eliminates the problem of version skew.
You should now be able to upgrade to the raring version of ia32-libs
without problem.
