Please try the attached (untested) patch.
/torkel
Index: fai-chboot
===================================================================
--- fai-chboot (revision 3540)
+++ fai-chboot (working copy)
@@ -251,6 +251,10 @@
# rename network config file
my ($host) = shift;
my ($ipadr,$hex) = host2hex($host);
+ if (! -e "$pxedir/$hex") {
+ print "$host ($hex) is not enabled\n";
+ return;
+ }
print "disable pxe config for $host in hex $hex\n" if $verbose;
return if $opt_n;
rename "$pxedir/$hex","$pxedir/$hex.disable" or $error .= "\nRename for $hex failed. $! $@";