I've looked but haven't found anything in the forums or on launchpad.net yet. All previous Ubuntu versions work fine using grub2 to loopback mount the .iso image to try out the newer versions without requiring either a USB stick image or burning a dvd/cd.

When I boot the iso images using grub2 on a usb stick they work ok.

When I try to boot the iso images using grub2 on a sata disk I get the following errors and then it drops to busybox:

ata1.00: qc timeout (cmd 0xec)
ata1.00: failed to identify (I/O error err_mask=0x4)

There may be some kernel parameters I can pass but I'm not sure what to try. Any ideas?