I am facing problem when working with Google Earth imagery. When I am digitizing at 1:1000 it just shifts the shapefiles when I even pan the image. Checked for CRS and everything but it doesn't work for me.
You might be running into an well known Issue: http://hub.qgis.org/issues/6822
Please see this question:How to Digitize Free Satellite Imagery in QGIS - Alignment issues with Openlayers Plugin