When encountering QuickBooks error 6143, users typically face issues with opening their company files. This error can arise from a variety of sources including damaged company files, incorrect network setup, or conflicts with the background processes on the computer. It's crucial to ensure that QuickBooks is up-to-date and that the network settings are correctly configured for optimal performance. Regular backups and maintenance of company files can help prevent this error. For troubleshooting, users can try opening the file directly from the server or using the QuickBooks File Doctor tool.