Hey, Ismael and Yigit, thanks for your support but I already found the solution, it was embarrasingly easy!
The last three of my slides had the following code with different text variations:

<style>
ul.b {list-style-type:square;}
p.ex1 {margin-top:1cm;}
</style>
<ul class="b"> 
<li style="color: #FFC000"><font color="#615e5e">Nuestro equipamiento y software de análisis estadístico nos permiten realizar <b>encuestas y relevamientos geo-referenciados. </b> Acoplando bases de datos y sistemas de representación cartográfica exponemos información espacial y temática en forma integrada.
</font></li>
<li style="margin-top: 15px; color: #FFC000"><font color="#615e5e">Los informes geo-referenciados permiten <b>reconocer tendencias y patrones que serían indetectables con otros medios</b>,  por ello constituyen un aporte valioso al análisis situacional y al diseño estratégico.</li></ul>

The problem was that i had forgotten to put </font> at the last sentence!! For some crazy reason the result was that the fourth slide wouldn’t show -it didnt matter which slide it was, as long it wasn’t in the fourth place. As soon as i wrote </font> and saved it everything started working again. Thanks for your help, I’m very happy with Enfold!