I have reconfigured my mce.ini using the custom LED notificaitons and all of them are fine, apart from the "Device On" light, which (intermittently, I might add) changes from a pulsing white light to a faint and very dim red light, following the same pattern as dicated for the white light. Usually all I have to do is unlock the screen using the slider and re-lock it, maybe once or twice, to start the LED working as required again.

It could be a broken pattern in mce.ini.

Have you changed it at all using custom LED / vibration applications?