We have the Mid 2012 MacBook Pro's.

We have the problems sometimes if you netboot too many at once.

Try shrinking the netboot images. When I make my netboot image I run this script when I'm done and it shrinks it down and makes things a little better.

#!/bin/bash

# Very unsophisticated script to trim down a Casper NetBoot.dmg file inside a .nbi folder
# Author : r.purves@arts.ac.uk
# Version : 1.0 - Initial Version

# REQUIRES that the NetBoot.dmg file inside the .nbi file be mounted before use!
# REQUIRES that the NetBoot.dmg have the volume name of "Macintosh HD 1"

# Start by setting up the array variable to hold all the files and folders we're going to delete

delete[0]="/Library/Preferences/SystemConfiguration/preferences.plist"
delete[1]="/Library/Updates/"
delete[2]="/Library/Desktop Pictures/Antelope Canyon.jpg"
delete[3]="/Library/Desktop Pictures/Bahamas Aerial.jpg"
delete[4]="/Library/Desktop Pictures/Beach.jpg"
delete[5]="/Library/Desktop Pictures/Blue Pond.jpg"
delete[6]="/Library/Desktop Pictures/Bristle Grass.jpg"
delete[7]="/Library/Desktop Pictures/Brushes.jpg"
delete[8]="/Library/Desktop Pictures/Circles.jpg"
delete[9]="/Library/Desktop Pictures/Ducks on a Misty Pond.jpg"
delete[10]="/Library/Desktop Pictures/Eagle & Waterfall.jpg"
delete[11]="/Library/Desktop Pictures/Earth and Moon.jpg"
delete[12]="/Library/Desktop Pictures/Earth Horizon.jpg"
delete[13]="/Library/Desktop Pictures/Elephant.jpg"
delete[14]="/Library/Desktop Pictures/Flamingos.jpg"
delete[15]="/Library/Desktop Pictures/Floating Ice.jpg"
delete[16]="/Library/Desktop Pictures/Floating Leaves.jpg"
delete[17]="/Library/Desktop Pictures/Forest in Mist.jpg"
delete[18]="/Library/Desktop Pictures/Frog.jpg"
delete[19]="/Library/Desktop Pictures/Galaxy.jpg"
delete[20]="/Library/Desktop Pictures/Grass Blades.jpg"
delete[21]="/Library/Desktop Pictures/Hawaiian Print.jpg"
delete[22]="/Library/Desktop Pictures/Isles.jpg"
delete[23]="/Library/Desktop Pictures/Lake.jpg"
delete[24]="/Library/Desktop Pictures/Lion.jpg"
delete[25]="/Library/Desktop Pictures/Milky Way.jpg"
delete[26]="/Library/Desktop Pictures/Moon.jpg"
delete[27]="/Library/Desktop Pictures/Mt. Fuji.jpg"
delete[28]="/Library/Desktop Pictures/Pink Forest.jpg"
delete[29]="/Library/Desktop Pictures/Pink Lotus Flower.jpg"
delete[30]="/Library/Desktop Pictures/Poppies.jpg"
delete[31]="/Library/Desktop Pictures/Red Bells.jpg"
delete[32]="/Library/Desktop Pictures/Rice Paddy.jpg"
delete[33]="/Library/Desktop Pictures/Shapes.jpg"
delete[34]="/Library/Desktop Pictures/Sky.jpg"
delete[35]="/Library/Desktop Pictures/Snow.jpg"
delete[36]="/Library/Desktop Pictures/Zebras.jpg"
delete[37]="/Library/Desktop Pictures/Solid Colours/"
delete[38]="/Library/Application Support/CrashReporter/"
delete[39]="/Library/QuickLook/"
delete[40]="/private/var/db/dyld/"
delete[41]="/usr/share/man/"
delete[42]="/usr/share/emacs"?
delete[43]="/usr/share/vim"
delete[44]="/usr/share/cups"
delete[45]="/usr/share/doc"
delete[46]="/System/Library/Address Book Plug-Ins/"
delete[47]="/System/Library/Automator/"
delete[48]="/System/Library/Speech/"
delete[49]="/System/Library/User Template/"
delete[50]="/System/Library/Caches/"
delete[51]="/System/Library/Screen Savers/"
delete[52]="/System/Library/CoreServices/RawCamera.bundle"
delete[53]="/usr/X11/"
delete[54]="/usr/libexec/cups/"
delete[55]="/System/Library/Input Methods/CharacterPalette.app"
delete[56]="/System/Library/Input Methods/InkServer.app"
delete[57]="/System/Library/Input Methods/50onPaletteServer.app"
delete[58]="/System/Library/Input Methods/KoreanIM.app"
delete[59]="/System/Library/Input Methods/Kotoeri.app"
delete[60]="/System/Library/Input Methods/PluginIM.app"
delete[61]="/System/Library/Input Methods/SCIM.app"
delete[62]="/System/Library/Input Methods/TamilIM.app"
delete[63]="/System/Library/Input Methods/TCIM.app"
delete[64]="/System/Library/Input Methods/VietnameseIM.app"
delete[65]="/System/Library/CoreServices/Encodings/"
delete[66]="/private/var/log/"
delete[67]="/Library/Internet Plug-Ins/"
delete[68]="/Library/Perl"
delete[69]="/Library/Receipts/"
delete[70]="/usr/bin/php"
delete[71]="/Library/Application Support/CrashReporter"
delete[72]="/Library/Application Support/iLifeMediaBrowser"
delete[73]="/Library/Application Support/Macromedia"
delete[74]="/Library/Application Support/ProApps"
delete[75]="/Library/Audio/"
delete[76]="/Library/Dictionaries/"
delete[77]="/Library/Documentation/"
delete[78]="/Library/iTunes/"
delete[79]="/Library/Logs/"
delete[80]="/Library/Modem Scripts/"
delete[81]="/Library/PDF Services/"
delete[82]="/Library/Scripts/"
delete[83]="/Library/Spotlight/"
delete[84]="/Library/User Pictures/"
delete[85]="/Library/WebServer/"
delete[86]="/Library/Widgets/"
delete[87]="/usr/bin/emacs"
delete[88]="/usr/bin/emacs-undumped"
delete[89]="/Library/Application Support/Apple/Mail"
delete[90]="/Library/Application Support/Apple/Grapher"
delete[91]="/Library/Application Support/Apple/iChat Icons"
delete[92]="/Library/Application Support/Apple/Automator"
delete[93]="/Library/Printers/"
delete[94]="/Library/Image Capture/"
delete[95]="/private/var/vm/sleepimage"
delete[96]="/private/var/vm/swapfile*"

# Let's do the deleting!

# Calculate the length of the delete array.
# 61 when I created it. 96 now. May have changed since.

tLen=${#delete[@]}

# Loop around the array and delete the files/folders.

for (( i=0; i<${tLen}; i++ ));
do
echo "Now deleting /Volumes/Macintosh HD 1"${delete[$i]}
rm -rf /Volumes/Macintosh HD 1${delete[$i]}
done

exit 0

From what I understand, the 2011 hardware uses 512byte blocks to transfer via TFTP where as older AND newer hardware uses 8192. I will try your script and see if it helps!

Thank you!

I've seen that behavior, not just on the 2011, but also on the 2009 and 2010 models as well. I haven't spent a bunch of time troubleshooting it. The only work around that I've found is to boot from an USB hard drive, select the NBI in Startup Disks, and then re-boot. I'm able to get the machines to NB that way.