Addition: after installing powernowd package, which implied removing the cpufreqd package, CPU frequency scaling works again on my Athlon X2 6000+. So the problem seems to be related to cpufreqd.
Addition: after installing powernowd package, which implied removing the cpufreqd package, CPU frequency scaling works again on my Athlon X2 6000+. So the problem seems to be related to cpufreqd.