I have 6 images that are 300dpi 3586x2889 and are around 3mb's each. The thumbnailer did not work them (i tested a smaller 72dpi jpg with thumbnail succes) so I made my own 72dpi 100px wide thumbs for the images. Everything displays as expected in Mac OS X Safari, but when I view them in Windows IE6 and Windows Firefox Filebrowser showed broken image icons for the main images AND the thumbs. The SAVE feature worked as expected on windows.
I was looking in the forum for anything related without luck.
I used Photoshop CS2 to save the 300 dpi jpg's down to 100 px wide 72 dpi thumbs. The original hi res jpg's were exported out of Illustrator CS2 then brought into .. AHH I just thought of something. They're saved as CMYK. I'll try to save as RGB and see what happens.