What operating system (Windows / Mac / other)? Is this your personal computer or a computer owned and maintained by an institution? What antivirus or malware prevention software are you using, if any? Describe in more detail what you mean by "transferring data". Which settings gear icon? Is this a Mac to Mac movement using Migration Assistant? Did you report the exact words of the error message or a summary? Have you regularly been syncing your library online to the Zotero website under the luke0210 username (or some other name)?