Some of the errors i can see why, but when you look through the code from the very start there are special characters in the XML tags.
Looking at for example the first product in your XML lines 10 - 21
<item>
<title><![CDATA[10 x 7 Flyer]]></title>
<link><![CDATA[http://promoprinto.com/index.php?page=shop.product_details&flypage=shop.flypage&option=com_virtuemart&product_id=40]]></link>
<description><![CDATA[The best way to advertise your business or event is with our premium UV Coated postcards and flyers.]]></description>
<g:image_link><![CDATA[http://promoprinto.com/components/com_virtuemart/shop_image/product/f863ec1a976e5d122570593fc4e9b44e.jpg]]></g:image_link>
<g:mpn>FL_4/4_10x7</g:mpn>
<g:brand><![CDATA[PromoPrinto.com]]></g:brand>
<g:id>40</g:id>
<g:currency>USD</g:currency>
<g

rice>639.99</g

rice>
<g

roduct_type><![CDATA[Flyers]]></g

roduct_type>
<g:condition>New</g:condition>
</item>
You can see
<g:mpn>FL_4/4_10x7</g:mpn>
The / and the _ are both counted as special characters. No XML accepts special characters so the XML becomes invalid. I am looking at ways to encode the special characters into the XML as this thread talks about here
http://groups.google.com/group/base-help-bulk/browse_thread/thread/43c9b32c3276f9ae?tvc=2
(not sure if that will make much sense to you)
Basically the Mambot needs to be made to have a recoding section, that detects there is a special character in the text to be add to the XML, and then encodes that specific character.
That is to be added to the next version of my feed, but is not available in this one yet.
This is why i always ask everywhere on the site to try the demo version first, the solution is to remove all special charactors from the titles and short descripption. I will try and get an accrute time scale of when the next version will be released for you.