I'm seeing the same error with both i386 & amd64 also. Have tried i386 on my old test laptop (Compaq Armada M700 with PXE boot nic) and a new(ish) P4 on a Gigabyte GA-945GM-S2 motherboard with an onboard Realtek Gbit nic.
If i select Gutsy 7.10 i386, (k)ubuntu PXE loads fine. I'm only seeing the error with Hardy Heron 8.04 i386 & amd64.
I can confirm this as a problem too. I've tried to preseed the install from an already installed system without any luck.
The logs indicate that anna has set the apt-mirror-setup to be installed later. I can confirm that the package was downloaded successfully, and pressing enter 3 times to get back on track with the installer works fine.
Thank you for reporting this bug. Have you checked the md5 sum of the iso file?