Comment 26 for bug 215074

I can confirm that this annoying bug has been present for a while now and is still present in 10.04 on my second generation macbook.

Booting into OSX fixes the issue. My guess is that something related to suspend/resume triggers it, also the connection to the external power supply might be of influence. IIRC, I could trigger this behaviour by suspending while connected to the powersupply, disconnect, resume. Maybe someone else can confirm this or play around.