Cause: You have multicollinearity (two variables correlate perfectly) or insufficient sample size. Fix: Check for duplicate variables or reduce your number of free parameters.
Students frequently encounter "Fatal Error" messages. Here is a cheat sheet: lisrel student version
The short answer: Yes, for 80% of theses. lisrel student version
Most Master's theses in Psychology, Business, or Education test models with 3 to 5 latent variables, each measured by 3 to 5 items (15-25 observed variables total). The LISREL Student Version handles this easily. lisrel student version
When to upgrade to Full LISREL (or rent a cloud version):