Do you have the thumbnail panel set to show the thumbnail at 640 pixels?
Do you have the image selected when you tell it to rebuild?
Do you see any activity in the bottom panel (click the dot/plus sign on the bottom left of the main window.)
#3 with windows XP the plus signs (loupe) are in the upper right hand corner. But no activity there.
Sizes of thumbnails do not changeto 640. If I click on the plus signs, the grey boxes get bigger, but thumbnails stay the same size.
I made screenshots. How can I upload screenshot in this forum?