Yesterday I added "unstable" to my apt.sources and did an upgrade.
Now I get a kernel panic, dropping into a debugger on boot. This only happens with Paul M's 2.2.15pre19 kernel - it does not happen with the older 2.2.15.pre14 kernel. It seems to be setserial that's the problem, removing this package cured it. Since my Powerbook doesn't have any serial ports, I'm not sure what it was doing there anyway - I don't remember deliberately installing it. Stephen