Hi,
that’s because the shield was added in 2.0.4400 I think, so you don’t see the CPU usage using the old version because it doesn’t have that shield yet. That can mean that you still might have the app(s) that keeps writing to the SD card, you just don’t know now. If you disable all the shields in the current version and the problem persist (even after reboot), we should investigate more cause I can’t think of any other valid reason for the high CPU usage.
Filip