The discussion revolves around resolving an MCNP5 error related to the IMCN routine, specifically a memory issue linked to source particles. Users suggest searching for the error message online and reviewing input files for trailing spaces and blank lines, which may cause problems. One participant notes that changing certain lines to comment format can help, while another mentions that ENDF VIII might be incompatible with older MCNP5 versions. The conversation highlights the importance of checking output files for detailed error messages and the potential need for specific library installations. Overall, the thread emphasizes troubleshooting techniques and compatibility considerations for MCNP5 users.