For better or for worse, I am making UBCD V4.0 available for download today after a short beta test.
This released is based on syslinux/isolinux instead of CDShell. I am abandoning the latter due to its lack of further development, while syslinux/isolinux is still undergoing active development, so there is a better chance that syslinux/isolinux will work with newer machines.
There is also experimental support for running UBCD from a USB memory stick via a modified version of the UBCD2USB script, which has lurked around in the forum for quite a while now.
For the full details of this release, please refer to http://www.ultimatebootcd.com/history.html