I have a strange issue... all clues/help appreciated!

I have a mediapicker property on a page that selects an album in the media section, all images below are listed as thumbs (works nicely), and also shown as a larger version in a lightbox.

Link to the resized image:

Screenshot of the same image shown in the lightbox:

xslt code:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE xsl:stylesheet [ <!ENTITY nbsp "&#x00A0;"> ]>
<xsl:stylesheet
  version="1.0"
  xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
  xmlns:msxml="urn:schemas-microsoft-com:xslt"
  xmlns:umbraco.library="urn:umbraco.library" xmlns:Exslt.ExsltCommon="urn:Exslt.ExsltCommon" xmlns:Exslt.ExsltDatesAndTimes="urn:Exslt.ExsltDatesAndTimes" xmlns:Exslt.ExsltMath="urn:Exslt.ExsltMath" xmlns:Exslt.ExsltRegularExpressions="urn:Exslt.ExsltRegularExpressions" xmlns:Exslt.ExsltStrings="urn:Exslt.ExsltStrings" xmlns:Exslt.ExsltSets="urn:Exslt.ExsltSets"
  exclude-result-prefixes="msxml
 umbraco.library Exslt.ExsltCommon Exslt.ExsltDatesAndTimes 
Exslt.ExsltMath Exslt.ExsltRegularExpressions Exslt.ExsltStrings 
Exslt.ExsltSets ">


<xsl:output method="xml" omit-xml-declaration="yes"/>

<xsl:param name="currentPage"/>
<xsl:variable name="mediapickerproperty" select="$currentPage/imageLibrary"/> <!-- datatype property for the mediapicker -->
<xsl:variable name="bigW" select="700"/> <!-- max width of lightbox popup image in pixels -->
<xsl:variable name="bigH" select="700"/> <!-- max height of lightbox popup image in pixels -->    
    
<xsl:template match="/">

  <xsl:if test="$mediapickerproperty &gt; 0">
    <xsl:variable name="images" select="umbraco.library:GetMedia($mediapickerproperty, 1)" />
    <xsl:if test="count($images/*) &gt; 0">
      <xsl:for-each select="$images/*">
   <xsl:if test="./umbracoFile != ''">


<div class="thumbback">
<a>
    <xsl:attribute name= "class">fancybox gallery</xsl:attribute>
    <xsl:attribute name= "rel">group</xsl:attribute>

      <xsl:choose>
         <xsl:when test="./umbracoWidth &lt; 700 and ./umbracoHeight &lt; 700">
      <xsl:attribute name= "href">
        <xsl:value-of select="./umbracoFile"/>
        </xsl:attribute>
      </xsl:when>
      <xsl:when test="./umbracoWidth &gt; ./umbracoHeight"> <!-- scale based on height OR width -->
      <xsl:attribute name= "href">
        /umbraco/imageGen.aspx?image=<xsl:value-of select="./umbracoFile"/>&amp;width=<xsl:value-of select="$bigW"/>&amp;constrain=true
        </xsl:attribute>
      </xsl:when>
      <xsl:otherwise>
      <xsl:attribute name= "href">
        /umbraco/imageGen.aspx?image=<xsl:value-of select="./umbracoFile"/>&amp;height=<xsl:value-of select="$bigH"/>&amp;constrain=true
        </xsl:attribute>
      </xsl:otherwise>
    </xsl:choose>  <!--Small thumbnail -->
        <img src="/umbraco/ImageGen.ashx?image={./umbracoFile}&amp;height=75&amp;width=75&amp;pad=true&amp;bgcolor=ffffff" alt="{./ImgDescription}" title="{./ImgDescription}"/>    
     </a></div>
        </xsl:if>
      </xsl:for-each>
    </xsl:if>
  </xsl:if>

</xsl:template>

</xsl:stylesheet>