Thanks for the detailed description, Toby. (Are the dev-info and/or FAQ gnomes gathering this?)

I managed to try the tuner without Hijack last night; the good (and bad!) news is that it worked beatifully, going from Dormant into Active within a couple of seconds, and doing everything it should.

Sometimes after changing to a different preset, or on power-up, it remains stuck in Dormant, and I have to change the frequency one notch and back again for it to work. Perhaps there's a subtle race condition - is the AF code getting the frequencies too quickly, before it's reset itself?

I'm surprised that reverting to the stock kernel made a difference (I haven't entirely ruled out coincidence, but it's looking suspicious. I do want to be certain before emabarking on the heresy of suggesting HJ's not perfect, though!) I'm now running the oldest Hijack I have (v221) in the hope that we can identify what's upsetting it.