Large modules are often split up into smaller pieces to make them easier to load. Your host's Digest::MD5 has been autosplit, which is why it's looking in auto/.
This isn't something you can fix... Digest::MD5 has to be compiled on the server.
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.