Got a startup cable for my thunder last week, im running it on a cx2 and all is fine.
I've got a mate who's had some issues with his so tonight I started doing some tests.

With me already running a hawk id just been using my current cables. But it turns out that the adapter cable that came with the thunder isn't compatible with the startup cable!? It tries to start but wont at all with a cartridge in and only just ticks over without one.
It works fine with the old hawk adapter cable though.

Seems a bit backwards. But its the same for mine and my mates.