First, appologies - I'm running in Windows Server 2012 in IIS 8.5 and not in any LAMP emulation, PHP manually installed, MySQL running normally. I'm also using the NTLMActiveDirectory extension to authenticate my users against AD and create accounts automatically. I have a question on that extension's talk page for assistance in case it is related.
My symptoms are:
All functions appear to be working normally, including creating/changing/saving pages, however the upload file process results in a "Sorry! We could not process your edit due to a loss of session data." failure. I am not getting this error when using anything except file uploads.
When connected to the host server and using the same upload link via a localhost connection, the file saves perfectly fine.
Permissions appear to be granted properly to the PHP and web folders and I can see that the PHP session folder is populating with files, but uploads do not work outside of localhost.
This is the only clue I have to go on at this point, so I was hoping someone could point me in the right direction. I'm assuming there's a possability that the NTLMActiveDirectory plugin is in play, but that doesn't explain why things work fine (and are also authenticated properly) when on localhost.
So, sorry that this is a windows question, but my hands are mostly tied in terms of the environment available for this project.