Definitely need to look into that 777 recommendation. I am not happy with that.
OK – I have found the source of the error and sadly it is in the minimised javascript code that is the plupload component – which is a third party library.
So it is not coning from Simple:Press but coming from the script library we hand off to to perform the actual upload.
It looks to me, like the really important part of the message is probably the HTTP_ERROR part – not the rest. The rest of the message, I am thinking, is probably just a sort of best guess the script is making at the most likely reason why there would be an HTTP request failure.
So this actually looks more like your server denying the HTTP request than anything else. To diagnose this you might need to access the http logs as they should, I would hope, provide a little more detail – like the status code for starters. Or – if I were you 0 have a word with your hosting support and explain the symptoms and the http failure.
One thing does spring to mind though. Does it have anything at all to do with the file name? I am assuming here that your user and yourself were using different filenames so this is unlikely. I ask simply because having something like mod_security active might throw out requests that match certain black-listed patterns.