I get this ringing overtone when I strum some open chords and it's kind of annoying. I get it with a G chord allot. It is coming from the g b and high e strings. I am not sure if this is normal or not.
I was watching this youtube video and noticed this guy has the same ringing overtone when he is strumming so I am posting it as a example of what I mean. Turn up the volume and really listen to the trebble strings....happens around 7:50 of the video when he starts strumming.

Does it happen on your guitar too?
Not overtones, just the treble strings ringing as they get struck. If it's too much for you, lower the treble side of your pickup a bit to balance the low & high strings out a bit. BTW he uses way too much elbow for this, you'll get awfull damned tired using your lower arm all the time & it's harder to switch back & forth between strumming & picking notes whne your flailing away like that. I guess anybody can give lessons these days with You Tube. Try Guitar Player TV or True Fire TV for quality free lessons.
Moving on.....
I was playing around with my guitar this morning and the high pitched ringing sound is coming from the g string when played open. I notice it ringing like in the video when playing chords like Em G and C where the g sting is played open.
I tried putting my finger on the g string past the nut and near the headstock but it still happens. Still not sure if this is normal or not.