I'm having a problem uploading files into WordPress. I recently updated to 3.3.1 and had no problems uploading anything until a week and a half later. There have been no plugins added, removed or updated. Smaller files (<~2.5) upload fine. Larger files (6MB+) refuse to upload. The files are being uploaded onto the server and they do exist, but WordPress returns a 500 Internal Server Error with the message: "Unknown post type.", and do not show up in the media list. Instead, the loading bar freezes on "Crunching" after the file has been uploaded.
I'd appreciate any information that can help fix this problem. I can supply any extra information needed.