The rc.d directory is fine, and tivowebplus did try and start.
The only obvious thing I could suggest is it might be a bad TWP install, but doesn't really explain why it works when manually started.
Does tivoweb.log look normal if started manually.
Try downloading the newest zip from tivowebplus and follow the instructions on that page for installation.
Other then that, I'll leave the TWP troubleshooting up to Thomson, as it's his baby.
Peter.