Just had a thought, Swithin. When you say "post from your computer", are you attempting to post them as full photos, or as attachments to your post - as you would an email?
I noticed in your "Hometown Photos" thread, your posting them as thumbnail attachments. There is a limit on these here. The limit is 3MB. You can post many small images, or a handful of large images, but the total bytes puts a cap on our posting. I started a thread on this many months ago (April 28, 2014 - nearly a full year ago) and it has never been addressed, so I just post web images, or my own which I have run through a web photo hosting site to obtain a postable URL.
One other work-around you may wish to use; it involves deleting previous thumbnails to free up space for posting new thumbnails. This pretty much renders your earlier posts useless - that's why I don't use this method.
See the original post here: