I am confused that you say you get the message when booting from lilo or the install disc... is that really what you meant?
A couple of stabs in the dark:
Are your device nodes different on the new box? If so then it is likely that your root or boot partitions are not being mounted correctly. There is a discussion of a similar problem
here.
Also, since you rsynced from one box to another you almost certainly have different devices on the new box and you will likely need different lilo parameters, a different initrd if you use one, different modules and kernel support - could be a lot of things along those lines... and you will need to actually run lilo before you can boot to it...
But that brings us back to why you cannot boot to the install disk - can you be more specific about that?