Hi everyone,

Thank you all so much for your replies and suggestions! I just wanted to let you know that I finally managed to get it working.

For anyone else who might run into this "3D Error" in the future, here is exactly what fixed it for me: I uninstalled my current version, installed the 32-bit version of Sweet Home 3D instead, and then added the SweetHome3D.l4j.ini file into the program's installation folder. That combination worked like a charm, and the program opens without any errors now.

Thanks again for your time and help!