Been a while since I played this, so I don't remember the details at all.

However, Minotaurs are one of the stronger enemies, ya? Perhaps you have to damage them a bit (or a lot) before the petrification will be effective. Also, according to the 'real' legend, medusa can only petrify you if you look at her. So don't shoot the thing at their backs!

Otherwise, I 2nd the glitch idea.