[Plugin: NextGEN Gallery] First image in slideshow flashes,

Hello,
I am still lost with this error:
the first image of the slideshow appears for half a second, then nothing, then appears normally. At the end of the slideshow, again nothing appears between the last and the first image.
I had this issue now a couple of times, made sure that the code is inserted correctly (no formatting), changed the images, emptied the cache, tried another gallery, disabled other plugins… nothing. There is no empty image in that gallery.
I see that others have that issue sporadically too. Would be great to get this resolved.
Thx

http://wordpress.org/extend/plugins/nextgen-gallery/