Sorry for my bad english... I've the same problem, which DIDN'T appear in the ALPHA release. This bug is shown only in the BETA WHEEZY release. If there is a non-free firmware, the installer stopped the installation. A solution can be insert a USB pendrive with the firmwares, it works for me.
Please, solve this bug, it's very important in my opinion. -- To UNSUBSCRIBE, email to debian-bugs-dist-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org