Netboot issues

So, I got my terminal connected, now I'm trying to netboot 2.1 on this 
4000/VLC. The last time I did this, I had no problems at all netbooting 
1.5 on it. Now, it seems that the MOP bootloader is, well.. "Invalid."

?50 SCB2NDINT ESA0
  83 BOOT SYS

This is the message that awaits me after running "b esa0" or "b/100 esa0"

Since I successfully netbooted during the 1.5 days, I took the "boot.mop" 
file from the 1.5 FTP directory, and lo and behold, it booted from that 
image just fine.

I did notice a major difference between the two files. The 1.5 loader is 
of the type "Native VAX" when checked by "mopchk" while the 2.1 loader is 
of the type "Elf32 VAX". I tried converting the new image using "mopcopy" 
but it made no difference, the image still gave the error listed above.

Yes, I have everything set up correctly as far as I can tell. The VLC 
requests the loader and is given it. It's just that the 2.1 loader seems 
like it's broken.