Solution to this problem seems to be to uninstall the ATI driver. It not only resolves the problem with the plymouth logo, but also means the system can auto-detect monitor type correctly, 3d effects are enabled [where supported] and as far as I can tell, run faster. More importantly though.. it stops corrupting the boot loader. So you can reboot more than just a few times before it all falls over. [note, you still have to reinstall a clean copy of the boot loader afterwards].
Solution to this problem seems to be to uninstall the ATI driver. It not only resolves the problem with the plymouth logo, but also means the system can auto-detect monitor type correctly, 3d effects are enabled [where supported] and as far as I can tell, run faster. More importantly though.. it stops corrupting the boot loader. So you can reboot more than just a few times before it all falls over. [note, you still have to reinstall a clean copy of the boot loader afterwards].
Sometimes, less is more.