This might be related to an antivirus or system guardian style program blocking the extraction of the '.dll' files to your system.
Try temporarily disabling any antivirus or defender application if present. Either way, download the Project 1999 Patch Files and extract them again into your Everquest directory overwriting all files asked. If you think you may have inadvertently patched the Titanium client to Live, then you should start the install process over with a clean install.
Here is a link to the Install Guide for reference.
Here is a post regarding the false-positive virus flagging of '.dll' files that some people have encountered.
It appears at least one other person has run into something similar
here.