Hmm. Strange. The file must have disappeared when I did a reupload, and it wasn't possible to upload again until I removed the existing attachment (which told me that the file didn't exist). Seems like there is some sort of bug there. This has happened to me once before as well.
Donate to UBBDev today to help aid in Operational, Server and Script Maintenance, and Development costs.
Please also see our parent organization VNC Web Services if you're in the need of a new UBB.threads Install or Upgrade, Site/Server Migrations, or Security and Coding Services.