It looks like your add to cart button is setup as just an add to cart link, it is not a submit button as part of a form. I'm not sure what your code for the more information template is setup, but it should be something similar to the following:
<table border="0" cellspacing="0" cellpadding="7">
<tr>
<td valign="top">
<table border="0" width="180" cellspacing="0" cellpadding="8">
<tr>
<td><font face="Verdana" size="1"><b>ShirtDawg.Com<br>
</b></font><font face="Verdana" size="1"><br>
ShirtDawg t-shirts are made in the U.S.A. with ultra soft
100% pre-shrunk cotton and weigh a meaty 6.1 oz. All shirts
feature a seamless collarette and shoulder-to-shoulder
tape, with a double-needle neck, sleeve and hem. Our
water-based inks leave a soft-hand feel on these medium to
light colored t-shirts. At ShirtDawg we stand firmly by our
products and you can see the quality for yourself in this
t-shirt we have made just for you! Wear it proudly!
</font></td>
</tr>
</table></td>
<td valign="top">
<form action="[-- SHOPPING_CART_URL Base --]/order.cgi" method="post">
<input type="hidden" name="storeid" value="[-- STORE.ID --]">
<input type="hidden" name="dbname" value="products">
<input type="hidden" name="function" value="add">
<input type="hidden" name="itemnum" value="[-- PRODUCT.RecordNumber --]">
<center><table cellspacing="10" border="0"><tr><td valign="top">
[-- IF PRODUCT.DisplayOrderingOptions --]
[-- IF PRODUCT.OptionText --][-- PRODUCT.OptionText --]<br>[-- END_IF --]
[-- Order_Option_Menu Column --]
[-- END_IF --]
</td><td style="background-color: #000000;"></td><td valign="top">
<b><font size="4">
<input type="submit" value="ADD TO CART" style="background-color: transparent; color: red; border: 0px; font-family: verdana;"></b>
</form>
<br>
[-- IF PRODUCT.DisplayPrice --]
[-- IF PRODUCT.SaleAmount --]
<strike>[-- PRODUCT.Price --]</strike> <b>[-- PRODUCT.SaleAmount --]</b>
[-- ELSE --]
[-- PRODUCT.Price --]
[-- END_IF --]
[-- END_IF --]</font></td></tr></table></center>
<a href="http://shirtdawg.com/images/ABLANKSHIRT-XL.jpg" rel="lightbox" title="BLANK SHIRT"><img src="http://shirtdawg.com/images/ABLANKSHIRT-XL.jpg" border="0"></a> </td>
<td valign="top">[-- IF PRODUCT.Field3 --][-- PRODUCT.Field3 --][-- END_IF --]</td>
</tr>
</table>
You can use the following cookbook page as a guideline for setting up the add to cart form.
http://www.shopsite.com/templates/cookb ... -add.shtml