Models shift in Sim mode

[Duckie24]

All of a sudden my models all shift to the right when I go to sim mode.  Viz has been working perfectly and then "BAM" this started all of a sudden last night.  No known changes were made to Viz or the background, back all of my models are shifted equally to the right on the background when in sim mode.  On the Visualizer screen they are all in the proper place, so I'm not sure how to correct this since it only happens when I start the sim.  Am I missing something?

[PhilMassey]

Could the background image have been moved or deleted or changed in size.

[Duckie24]

Figured it out.  Set the resolution for background image on my large desktop monitor.  When I used the computer attached to a smaller monitor, the sim mode shrinks it to fit the screen, but does not adjust the placement of the props.  When I attached my computer to the large monitor again this evening, everything was back to normal.