Ok, I just managed, after much effort, to rebuild my USB key to install CentOS 6. There are a number of changes.
Partition the USB key, but make partition 1, Win 95 (FAT32) (I think that's partition type "b"), bigger. I made it 500M. The rest should be ext3 (or whatever).
Format the partitions. Make sure to toggle the bootable flag on partition 1.
syslinux /dev/<DOS partition>
When you're done, the DOS partition should look like this: ls -laF /mnt /boot/ /ldlinux.sys /syslinux/
Under /boot is /grub, and it's contents. Make sure you create a grub.conf to put in there. If syslinux didn't put it there, mount your .iso, and copy /mnt/iso/isolinux into there, then rename /syslinux/isolinus.cfg to /syslinux/syslinux.cfg. I put a grub.conf here, too: cat /mnt/disk/syslinux/grub.conf #debug --graphics default=0 splashimage=@SPLASHPATH@ timeout 5 hiddenmenu title @PRODUCT@ @VERSION@ kernel @KERNELPATH@ initrd @INITRDPATH@ title Install system with basic video driver kernel @KERNELPATH@ xdriver=vesa nomodeset askmethod initrd @INITRDPATH@ title rescue kernel @KERNELPATH@ rescue askmethod initrd @INITRDPATH@
On the second partition, copy your .iso images. Then copy /mnt/iso/images there.
You should be good to go.
NOTE: during the install, if you make any partitions encrypted, it will hang when it's done formatting, so reboot, and tell it to install again, and then not to format. It will start, then ask for the password, then actually go through the install.
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