Wow, Clive! Just . . . wow.
I feel your pain. It is amazing how LE 8 can work but a version of LE 9 won't. At any rate, if LE 9.1.7 is supposed to work you can download the update here:
Hopefully this will get you up & running.
(For a number of reasons I do not plan on upgrading to Mountain Lion. I'm running OSX 10.7.x and I think that's as far as I'm going. I really don't like the direction Apple are taking by making their OS more like their IOS used in their mobile devices.)
I know. I can only think Apple don't expect people to hang on to previous versions and failed to write LE 8 out of the picture...
The pain continues, I already found the download but it doesn't pick up the previous version so it won't upgrade. I'm in touch with Support and will report back on any solutions.