Comment 5 for bug 107516

I have the same thing on my thinkpad R40e. I found this bug on kernel.org so it looks like it isn't a ubuntu specific issue.

http://bugzilla.kernel.org/show_bug.cgi?id=8246

The good news is that as a workaround you can add ec_intr=0 to your kernel options. This worked for me. My system is back at full speed and battery monitor etc work fine, though I have to admit that I'm not sure what this option changes, but it's a better option than blacklisting the battery and ibm_acpi modules that I was doing before.