Nivo Slider effects are not working - slider

Question

I've searched and tried several of the solutions to no avail. I'm currently using jQuery 1.7.1 and Nivo Slider 3.0.1 .
You can see the website at http://www.wheelerbikeclub.net (this is a website I created last year and I'm just coming back to now).
None of the effects on my nivo slider in my home page are working. I know there was a point last year where they were, but then I changed something and now they don't and I cannot recollect what it is that happened.
I've made sure the number of columns/boxs/slices evenly divide my images. Does anyone have any idea what the issue is? Is it somehow related to the fact that I'm forcing my slider to cover the entire screen?
Thanks for any feedback, I greatly appreciate it!
I make calls for the jQuery followed by NivoSlider script in the head section
<script type="text/javascript" src="js/jquery-1.7.1.min.js"></script>
<script type="text/javascript" src="js/jquery.nivo.slider.3.0.1.js"></script>
<script type="text/javascript">
$(window).load(function() {
$('#slider').nivoSlider();
});
</script>
Then in my body in a wrapper I put
<div class="slider-wrapper theme-default">
<div id="slider" class="nivoSlider">
<img src="img/new_slides/slide_1-3.png" alt="" title="#slide_1-caption"/>
<img src="img/new_slides/slide_2-4.png" alt="" />
<img src="img/new_slides/slide_4.png" alt="" />
<img src="img/new_slides/slide_3-1.png" alt="" />
</div>
<div id="slide_1-caption" class="nivo-html-caption">
<strong>Find Out More</strong>.
</div>
</div>
There are four images and I'm just testing the caption with image one.
In my nivo-slider css I have (not the entirety, just where I think the problem might lay)
.nivoSlider img {
position:absolute;
top:0px;
left:0px;
z-index:2;
}
.nivo-slice {
display:block;
position:absolute;
z-index:100;
height:100%;
top:0;
}
.nivo-box {
display:block;
position:absolute;
z-index:5;
overflow:hidden;
}
.nivo-box img { display:block; }
And in my main styles.css I have
.slider-wrapper { position:relative;
top: 0px;
left: 0px;
width: 100%;
position:fixed;
z-index:0; }
#slider-div { min-height: 100%;
height: auto !important;
height: 100%;
margin: 0 auto -30px; }
Hope that makes sense.