Comment 27 for bug 649917

I had this problem on a seemingly standard setup, Asus P5K motherboard with quad core Core2 cpu and nvidia 7300. Here's my experience, in case it helps someone:

Booting from the maverick amd64 livecd off of a usb stick left me at the ubuntu logo with never-ending progress dots. Hitting escape revealed the "getpwid_r(): failed due to unknown user id" message, which was masking the real problem. Rebooting and choosing F6 during livecd bootup, and deleting the "quiet-splash" boot option revealed the true problem: "Buffer I/O Error on device, fd0 Logical Block 0". See http://ubuntuforums.org/showthread.php?t=1080102. My floppy controller was enabled in the BIOS, even though there's no floppy drive installed. This gave the kernel a fit. Disabling the controller in the BIOS allowed me to finally boot from the livecd. This has been reported in various places as a bug, but most of these are set as duplicates or fixed. Are any devs aware that it's still a problem?

https://bugzilla.kernel.org/show_bug.cgi?id=13486
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/236144
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/409094
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/384579