I replaced the IDE dvd/cd-drive with a new SATA drive, then tried to install again from the alpha-5 intrepid-alternate-amd64.iso. This time the installation went OK, so the conclusion is warranted that the problem was with recognizing my IDE dvd/cd-drive.
But note that there appears to be nothing wrong with this IDE drive: I managed to install Hardy with it using the hardy-alternate-amd64.iso, and a few weeks ago I installed Debian testing with it in another partition.
[On another note: the 2.6.27-amd64-2 kernel, once installed, also required the "acpi=off" boot option. After this kernel was upgraded to the -3 version, there appeared still a problem with vesafb (computer beeping a few times), then continuing to boot without any ill effects, it would seem. I'm not filing a bug on that.]
I replaced the IDE dvd/cd-drive with a new SATA drive, then tried to install again from the alpha-5 intrepid- alternate- amd64.iso. This time the installation went OK, so the conclusion is warranted that the problem was with recognizing my IDE dvd/cd-drive.
But note that there appears to be nothing wrong with this IDE drive: I managed to install Hardy with it using the hardy-alternate -amd64. iso, and a few weeks ago I installed Debian testing with it in another partition.
[On another note: the 2.6.27-amd64-2 kernel, once installed, also required the "acpi=off" boot option. After this kernel was upgraded to the -3 version, there appeared still a problem with vesafb (computer beeping a few times), then continuing to boot without any ill effects, it would seem. I'm not filing a bug on that.]