I have a 2010 official arduino ethernet shield connected to an official pre-Uno arduino from last year, in the openenergymonitor.org setup; i.e. it is sampling 5 analog inputs to determine household power usage (5 = 1 voltage + 2 solar CTs + 2 mains CTs)
I had it hooked to the wishield and working well, except the wishield would drop out a couple times a day. :(
So I figured the ethernet shield might work better, and hooked it up, and the power values went all wonky - generally much higher than they should have been. I stripped down the sketch to not do any networking, removed initialization etc, so the shield was just sitting there doing nothing. Same problem. Took the ethernet shield out of the stack, and the values went back to normal again, with the same sketch.
Is there anything about the ethernet shield which would affect analog readings? I can post the sketch if needed...