I think, I should work and I forgot either to load an acpi module (which would surprise me; acpi_cpufreq, ac and battery are loaded as well as governors) or the power management program I use is not able to manage this type of battery (I tried cpufreqd, powersaved, powernowd and powertweakd).
What do you think?
Honestly, I have no clue - this all seems quite weird, as I've never seen a situation where it doesn't detect the battery. Something might be messed up with your particular install, as I haven't heard of such an issue even with the Core 2 Duo MacBooks. You could try reinstalling - also, you may want to try the amd64 architecture Debian if you're running the i386 one now (the Core 2 Duo will run either) - and you could try i386 if you've been running amd64.
I only have a Core Duo (i386-only) MacBook, though, so I don't know much about Core 2 Duo quirks.
Tim