This is because of the css you have on that page:
#wrapper #body div p {
font-family: "MS Serif","New York",serif;
margin: auto;
position: relative;
width: 800px;
}
the width setting there makes all <p> tags 800px wide and the name of the product in the cart has a <p> tag around it.
You can probably remove that width attribute and set the width when you need to using a class instead of assigning it to all <p> tags like you do currently.