I think this is an issue with swf_upload, though not 100%, I've had a similar thing when uploading massive files (a few MB).
After uploading a large image, I get
Fatal error: Class '' not found in /home/user/public_html/sapphire/filesystem/Folder.php on line 70
Or am I being haunted by a devious ghost class?
I guess it's the image because it was all working fine prior to this.