Here is what I see. Your Photopost was installed by us in January. It worked fine for a couple months and now you say you have problems uploading pictures which suggests something changed.
When we suggest you remove jpegtran to test something it means remove completely. Your error above is you just removed the jpegtran off the end of the jpegtran command which still tells the program jpegtran still is there so lets run it
. The whole jpegtrran line just be removed in the global options
So either remove that whole line or place jpegtran back on that line. I will try uploading about 10 more pictures and they surely will upload fine so the issue remains whats special about these certain pics that have this issue.