Sounds like your not doing the OSInstall.mpg method, as it doesnt require a reboot to complete the install.

finder->go->goto folder

/Volumes/Mac OS X Install DVD/System/Installation/Packages

if thats the name of your dvd installer disc

and double click OSInstall.mpkg and install using this util

DO NOT REBOOT after the install is done, you'll have to upload your kext's and bootloader etc.