Cross-over distortion thanks to short circuit protection
The crossover distortion is caused by the fact that you've basically put two back-to-back diodes &mdash; the B-E junction of Q2 and the B-C junction of Q3 &mdash; in series with your load, and the forward voltage drop of these junctions prevents current from flowing through the load near the zero crossings.

Also, note that your current limiter will only work with positive output voltages; a proper design would work on both positive and negative output peaks. This is normally done by sensing the current directly in the output stage and reducing the drive to the output transistors if necessary.