There needs to be some secondary code in GLISD that tries other methods to identify a partition if there is no filesystem or it's just "unknown".
This bug also happens when there is a physical Truecrypt partition on the hard drive. And it seems to be the reason why the installer failed on my computer with the "Gentoo 2006.1 LiveCD".
Hello guys, Just to give you an update, we haven't forgotten this bug. But unfortunatly the additional code you are requesting is not likely for 2007.1. I would suggest partitioning yourselves manually before running the installer. As always, patches welcome to code this fix. I can say at this point without a patch it probably isn't going to get done anytime soon.
The installer is deprecated.