… after raising my cache to 5gb the number of displayed pictures has now crept up from 493 to 511 after 5 hrs! Seems it will be ages before all 5pictures are displayed, if ever.
I think the problem wd was aiming to solve by these thumbnails is replaced by a more frustrating one of not seeing all the pictures you want to see. my suggestion: marry the two; display all folders and pictures initially using dummy icons, gradually update the thumbnails as is being done now, but give priority to any pictures on demand.
