the problem is, that apple efi is not compatible with windows uefi, so will get this error on some mac models with 64bit vistaa sp1, 64bit win7 and now with ubuntu too. the only way to fix this with windows is to create a new install dvd without efi, hopefully the ubuntu devs do not remove efi but try to support apple efi, if this can be done. otherwise please make the livecd not to boot efi on unsupported machines.
the problem is, that apple efi is not compatible with windows uefi, so will get this error on some mac models with 64bit vistaa sp1, 64bit win7 and now with ubuntu too. the only way to fix this with windows is to create a new install dvd without efi, hopefully the ubuntu devs do not remove efi but try to support apple efi, if this can be done. otherwise please make the livecd not to boot efi on unsupported machines.
best wishes, chief