Joerg, thanks for your information. This problem is caused because zlib1g 1:1.2.7.dfsg-11+b1 (amd64) and 1:1.2.7.dfsg-11 (i386) as available in wheezy are not co-installable. Install zlib1g from sid for both architectures and everything should be fine. This thing will be sorted out in time for the release. Cheers, -Hilko