Are you able to open the file from the web browsers ? What is the setup that you have on the PXE/TFTP server ?
I have seen a similar issues with IIS 7 not having the correct handling for a file with no extention or when the tftproot is not accessible for some reason.
I have seen a similar issue when the VM guest has the VMXNET3 adapter - it will get as far as the kickstart entry - if you go on to the console and manually try to set up the server you get a network error.
I would also check which storage adpater is used as I have hit issues with that too.
I too see a similar issue on one setup where it reaches till kickstart download from my IIS server while provisioning a physical Dell target. It fails with ‘Network Error – There was an error configuring your network interface’. Even manual 'Retry' does not help here with dynamic IP. The other console (Alt+F3) shows 'Error downloading <datastore URL for kickstart file as MAC>...iBFT doesn't couldn't provide valid NIC MAC address’. The same IIS is able to provide the kickstart from same datastore server while provisioning VM. Also another point is at this point where it fails, if I proceed with manual steps and provide static IP, it works well. Its a bit stange, suspect some problem with network.
Kate, what error do you see on screen and other console? Is it a physical target server or a target VM? Also, try the static IP as above and see if it works for you.