pencilart, under which system did you run your test?
If you're under Windows and the 3D view is all grey from time to time (most of the time after resizing the 3D view), I think it's more likely to be an other issue that happens only under Java 7/8. I spent a big part of the day trying to find a workaround, but without success.
Anyway, to finish better the day, I fixed an issue that was happening in Virtual visit mode for a high elevation of the viewpoint and made it available in the Beta 21. As the correction is a tradeoff that could alter the image quality of the 3D view (mainly on the borders of walls, furniture...), please check if it works for you.
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Emmanuel Puybaret, Sweet Home 3D creator
