This is probably due to the fact that you have to stop the print spooler to be able to install the print drivers and start it again when the installation is (almost) complete. This can be done either by creating custom actions or stop/start service ...
Just a little piece of advice; don't repackage Firefox, but use the redistributable msi from Frontmotion, and the downloadable .adm-files through GPO.http://www.frontmotion.com/Firefox/fmfirefox.htm
When setting permissions through the lockpermission table you can set perms on files and/or components only. If you want to set perms on a specific folder you have to set them on the component that creates that folder.
