sorry, don't mean to belabor the point, but just to be sure, you are on Antenna as described here?
http://www.ehow.com/how_7272934_tune-vizio-lcd-tv.html
from what I understand, Vizio's often don't have signal strength meters. does yours have one?
your signals are plenty strong, so it's not an antenna strength issue. omnis however are not always the best solultion
http://www.hdtvprimer.com/ANTENNAS/g...mnidirectional
are there any obstructions near the house?