I have the size limit set to 0 in usergroups. I'm thinking it's something with php timing out, though Photopost doesn't give any errors, it just returns to the gallery without uploading the image.
I remember Omega told me one time to put something about php in one of the files that tricked php into allowing more time so I didn't have to edit the php.ini file on the server. I did a search and could not find the thread again.
I don't if that same thing will fix this problem, but would like to give it a try. If you can remind me what that code was and where I am suppose to put it, I would be very greatful.
(I think I will bookmark it this time around for future uses too)