Keep in mind that other things can cause purple fringing beyond CA. The biggest culprit is light scattering on the sensor microlenses. That effect is prevalent on most small sensors with low pixel counts and has little to do with the lens being used....
Try setting the relay back to off again. It is possible that the two modes use a different format for the card, so if it is formated for one mode it won't work in the other. The other possibility is that when you did the switch the card got corrupted...
Try putting the camera into AVCHD mode first. On the G30 (which has a similar setup) the camera isn't recognized properly by the computer when it is in MP4 mode.
