Hi,
Besides the LVM corruption problem I mentioned in the other e-mail I also tried to install FC6 on a USB external HDD. I tried it first on Apple MacBook and I managed to install it successfully. However, I couldn't figure out how to get the MacBook to actually boot off of the USB drive. I thought maybe it was because grub might not have installed itself on the MBR of the USB HDD so - and there really is no good connection here - I decided to reinstall it on my desktop. However, after a few attempts I noticed that whenever I started up the FC6 install with my USB HDD attached and powered on Anaconda hung. I can attach it later on a running system and the HDD shows up on the desktop - though only the /boot folder shows up (Maybe LVM groups on an external drive aren't recognized?) I've since reinstalled it yet again on the MacBook and made sure grub installed to the MBR but haven't had any luck getting the MacBook to boot off of it yet.

My USB HDD is a Western Digital 150 GB.

udi = '/org/freedesktop/Hal/devices/usb_device_1058_404_57442D5743414C4C31373436363530'
  info.udi = '/org/freedesktop/Hal/devices/usb_device_1058_404_57442D5743414C4C31373436363530'  (string)
  linux.subsystem = 'usb'  (string)
  linux.hotplug_type = 1  (0x1)  (int)
  usb_device.bus_number = 3  (0x3)  (int)
  usb_device.can_wake_up = false  (bool)
  usb_device.is_self_powered = true  (bool)
  usb_device.version_bcd = 512  (0x200)  (int)
  usb_device.speed_bcd = 294912  (0x48000)  (int)
  usb_device.serial = '57442D5743414C4C31373436363530'  (string)
  usb_device.linux.device_number = 6  (0x6)  (int)
  usb_device.num_ports = 0  (0x0)  (int)
  usb_device.max_power = 100  (0x64)  (int)
  usb_device.device_revision_bcd = 1538  (0x602)  (int)
  info.product = 'External HDD'  (string)
  usb_device.product = 'External HDD'  (string)
  info.vendor = 'Western Digital Technologies, Inc.'  (string)
  usb_device.vendor = 'Western Digital Technologies, Inc.'  (string)
  usb_device.product_id = 1028  (0x404)  (int)
  usb_device.vendor_id = 4184  (0x1058)  (int)
  usb_device.device_protocol = 0  (0x0)  (int)
  usb_device.device_subclass = 0  (0x0)  (int)
  usb_device.device_class = 0  (0x0)  (int)
  usb_device.num_interfaces = 2  (0x2)  (int)
  usb_device.num_configurations = 1  (0x1)  (int)
  usb_device.configuration_value = 1  (0x1)  (int)
  usb_device.linux.sysfs_path = '/sys/devices/pci0000:00/0000:00:02.2/usb3/3-2'  (string)
  info.linux.driver = 'usb'  (string)
  info.bus = 'usb_device'  (string)
  info.parent = '/org/freedesktop/Hal/devices/usb_device_0_0_0000_00_02_2'  (string)
  linux.sysfs_path_device = '/sys/devices/pci0000:00/0000:00:02.2/usb3/3-2'  (string)
  linux.sysfs_path = '/sys/devices/pci0000:00/0000:00: 02.2/usb3/3-2'  (string)

Its on the USB3 bus which is an EHCI 2.00 controller on an nVidia nForce2 motherboard (Gigabyte GA-7N400 Pro2).