I have the identical problem with iWork '06.
I am also in the UK, not sure if it is a regional problem.
I will call Apple and find out if they can send a replacement.
Monster do a cable just for this purpose: Monster iStudioLink instrument adaptor, found on the Apple site, not too expensive.
I found a 3rd party cable that also works fine for about £6 (US$10). I use a Kramer Focus VT111S electric and have had no probs to date, although I think it would be...