Comment 9 for bug 120759

I had the same trouble after I upgraded to Gutsy. I did some homework and found out that yes speedstep-centrino is depricated in favor of acpi-cpufreq. One side effect of this, at least on my laptop, was that speedstep-centrino worked without SpeedStep being turned on in the BIOS. So when the new kernel was trying to load acpi-cpufreq it found that SpeedStep was disabled and didn't load it. That's why there weren't any errors.

So I went into the BIOS set SpeedStep to automatic and now it works flawlessly.
Hope this helps.