Message; "file does not exist"

We are suddenly having a problem with a disk-related file that manifests itself as "file does not exist". I changed these files to Memory-Related and that seemed to solve the problem but why? The files were not moved and previously had been working for the past 12 years.

Look at the Tmpdata directory - you may need to clean it out occasionally. If you see a lot of old temporary files, you may be running out of file names.