[syslinux] PXE question

[Jonathan]

Hello,

I run a cluster for computer game servers which are started on demand  
by users who book them. I have 15 nodes, some of them netbooted, some  
of them not. Recently i replaced a couple of old netbooted machines  
with new ones (with harddrives) for better performance. Inside the  
new boxes i used NICs from the old machines that i had taken out of  
the cluster and netboot.

A day or so after i had done it i checked back on the cluster to see  
if it was running okay, and noticed several of the netbooted nodes  
where down, so i went to the server room to investigate:

Each machine gets to the part where the kernel loads the PS/2 driver,  
and then the screen turns black, instantly.

What can cause this? I thought about network conflicts because i'd  
used NICs from the replaced machines, but disconnecting them and  
restarting the switch didn't help.

/Jonathan