I have been beating my brains out for over a week. I have a few models of Dell PC's that can no longer PXE boot to the LiteTouchPE_x64.wim image. However, the can boot to the 32 bit one.
What it does is it loads (slowly) the Boot image and as it gets ready to load it gives an error from Windows Boot Manager:
Windows failed to start. A recent hardware or software change might be the cause. Blah Blah
Info: The Application or operating system couldn't be loaded because the required file is missing or contains errors.
Different models show different missing files
Dell Optiplex 745's bxvbda.sys
Dell Optiplex 780's winload.exe
Both of these models were working previously and no changes were made to the server before the error occurred.