Weird issue with adjustments on Olympus E-P1 adjustments with my MBP 17" i7

Hi.

I have a very weird problem with Aperture on my MacBook Pro.

When I do adjustments on pictures (RAW from an E-P1), adjustment being (for now) auto-enhance and lighten shadows applied to a whole batch of pictures, the result picture is sometimes (could not find a pattern) totally "wrong", like overexposed of with colors totally off.

When that happens, if I reset all adjustments for the picture then undo the reset with COMMAND-Z, I get the correct, expected picture.

This is a total waste of time!
Anyone else experiencing this?

Thanks in advance,

Jérôme.