For those of you wanting to update to 10.6.4 with NBI, please note that there is a slight issues wiht NBI and large /System/Library/Extensions folders, the 10.6.4 undate increates this folder above the threshold, and so NBI is unable to regenerate the Extensions.mkext correctly. If you do update, please boot with recovery=y and run the fixed up version below:

http://dl.dropbox.com/u/863180/NetbookInstaller 20100616212351.app.zip

via NetbookInstaller + 10.6.4 « Meklorts Blog.