David - Your preview size setting has nothing to do with your 1:1 previews, just your standard size previews. 1:1 previews are generated automatically when you access a folder, at least in v1.0 and I haven't seen anything that says that changed for v1.1.
As Victoria has explained in the past, if you have your preview size set too small and Lightroom needs more pixels for a preview that it has available in your standard preview, it can finish up rendering 1:1 previews.
As I sometimes run in Library mode with the loupe selected and all four panels off 1680 pixel standard sized previews make sense with my 680x1050 monitor.
David
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