When you set the thumbnail size for the browser at 150x150 or 128x128, thumbnails of WDP images are only 90x90. If you set thumbs to 100x100, WDP images seem to be the right size, but the difference between 90 and 100 is difficult to tell. Smaller than 100x100 seems to work fine, and strangely enough, 192x192 seems to work fine. Unfortunately, 150x150 (or at least 128x128) is what works best for me.
I first noticed this issue in an older version (1.92(beta), I believe) and so i tried the current version (1.96.5) and the problem is still there.
