SAX ParseException error: expected )

Hello! i wish i could tell you versions, etc., but i am modifying code  for a webstore my boss is opening, and everything goes through IAModules. i'm not even allowed to see the .jsp files they're using, much less tinker with *them*. all store inventory data is xml, and the jsps wrap html around various xsl files, pulling data from the xml files.

i'm trying to get the product page to show certain text if the product selected is on sale, based on code found in IAModules' knowledgebase, but i keep getting 

<blockquote>
XSL Transform Error:
java.lang.Exception: org.xml.sax.SAXParseException: expected )
Message:org.xml.sax.SAXParseException: expected ) 
</blockquote>

i've checked and rechecked, i had others check and recheck, and no-one can find where the ) is missing. i know it's in the following block of code, because when i remove the one block, the page works (as original, though, not as what i want).

<code>
<xsl:choose>
   <xsl:when test="(number(.DisplayPrice) &lt; number(./Price4))">
      <p style="color:red; font-style:bold">On sale now! Regularly $<xsl:value-of select="./Price5" /></p>
      found sale<br /> <!-- just to reinforce, whilst testing -->
   </xsl:when>
   <xsl:otherwise>
      not on sale <br /> <!-- again, just for my reference whilst testing -->
   </xsl:otherwise>
</xsl:choose>
</code>

There's only one line with ( ) in it, and there are three complete pair there.

Can anyone see where i'm missing a )? or would know why *else* that error would get thrown?

i'd ask IAModules, but i'm afraid they'd see it as a chance to charge us for design-time. >P

Thank you!
aellath