Had to rename it because some "Flacon50.jpg" already existed (the scnd pic) but after that I had no problem uploading it:

...and the one that was already present on the server:

So it worked here: must be you or your system; just a hint: don't use space in the pics name (use _ or - or whatever you like) - it won't work until you replace the space by (I think) %20% in the tag...