Kirk,
That seems to have fixed the problem I described. Brilliant!
I believe it may have also partly - but not completely - fixed a related issue that I forgot to bring up. If I open a large contact sheet of CR2 files, and quickly unclick a star, I can sometimes get an incomplete filtered view. If I reset and reapply the filter, images missing in the first filtered view appear. This is very confusing because there is no way of knowing if all have been loaded or not. I can't always replicate this, perhaps because of caching? Again, this is not an issue with DNG files - in that case, it says "Filtering..." until all rating metadata has been loaded before displaying the filtered images.
thanks,
ethan