network install failed in EFI boot mode

I tried to install ubuntu-12.04.1-server-amd64 from network in EFI boot mode. And met a partition error:

The attempt to mount a file system with type vfat in SCSI3 (0,0,0), partition #1 (sda) at /boot/efi failed.
I did some investigation about this error, and found that the partman-auto can not support vfat format(If install my machine by cd, there is not this error). The preconfigure file is attached following, is there any errors in this file or ubuntu12.04.1 do not support this scenario?
Thanks.

the partition part in the preconfigure file:

d-i partman-auto/method strng regular
d-i partman-lvm/device_remove_lvm boolean true
d-i partman-md/device_remove_md boolean true

d-i partman-auto/disk string /dev/sda
d-i partman-auto/choose_recipe select atomic

# This makes partman automatically partition without confirmation, provided
# that you told it what to do using one of the methods above.

d-i partman/confirm_write_new_label boolean true
d-i partman/choose_partition select finish
d-i partman/confirm boolean true
d-i partman/confirm_nooverwrite boolean true