I just know enough to mess up my own installs, but I went looking through EVERYTHING that said plymouth and noticed in"/usr/sbin/plymouth-set-default-theme" something about "rebuild initrd". So instead of trying to rebuild initrd, I installed a new kernel.
I then had to use EZswitch to change to another theme, then use it to change back to the pclosedu.plymouth theme.
It worked on a reboot and again after a cold boot.
"The truth is somewhere out there".
I tried ezswitch, I tried change kernel and change again, I realized ezswitch does not work as I think is should : not so well that the command lines.
The command lines I use: I go to the directory /usr/share/plymouth/themes then cd again to the pclosedu theme. Then as root : "plymouth-set-default-theme name_of_the_theme", then once done, update initrd, as root, the command needs to use absolute path:
The script /usr/sbin/plymouth-set-default-theme which you talk about is called when invoking "plymouth-set-default-theme name_of_the_theme" as I just said above.
In my install the plymouth theme is working fine. The problem arises once the installed distro is remastered. I started to compare with the PCLinuxOS theme and the Lxde plymouth theme and found the permissions on files are different. I did a "chmod a-x" on the files of the pclosedu theme to make them identical and remastered again. If this is not enough, I'll try something else... or scream help to Timeth !
I was able to use EZswitch to set the correct plymouth theme, when logged in as root. I could not get EZswitch to work properly, when logged in as my normal user. By the way, RC8 is up and running on my HP Slimline.
Have you tried remastering after that ? If yes does it stick beyong remastering ? I wonder if I should not use the "boottheme" mylivecd option for remastering :?