Comment 4 for bug 152187

I had the same problem on a Toshiba R25. I poked around a little bit and it turns out the problem was introduced in kernel 2.6.21-rc4 and filed a kernel bug report:
http://bugzilla.kernel.org/show_bug.cgi?id=9487

Until it's fixed, the workaround I hinted at in the report (commenting that single line) works at least for my system. I'm pretty sure that it's NOT doing the right thing, though - to be honest I don't even understand what the code does.

I've made the workaround available as a kernel package that you might want to try - we'll find out if launchpad supports 20M attachments. But be sure you have a working kernel in case something goes horribly wrong - the package will replace the existing gutsy kernel image.