the report is complaining about the products results page, but the price fields should not have an issue there, they are validated to be numeric.
the issue should only be on the search page.
on the products search page, find the following two lines of code:
<input type="text" name="S_ProductPrice" id="S_ProductPrice" value="<?php echo((isset($_GET["S_ProductPrice"]))?$_GET["S_ProductPrice"]:"") ?>" size="10" onblur="if (document.getElementById('priceRangeServerValidation')) document.getElementById('priceRangeServerValidation').style.display='none';" style="width: 114px;" />
and:
<input name="S_ProductPrice2" type="text" id="S_ProductPrice2" onblur="if (document.getElementById('priceRangeServerValidation')) document.getElementById('priceRangeServerValidation').style.display='none';" value="<?php echo((isset($_GET["S_ProductPrice2"]))?$_GET["S_ProductPrice2"]:"") ?>" size="10" style="width: 114px;" />
and checnge them to:
<input type="text" name="S_ProductPrice" id="S_ProductPrice" value="<?php echo((isset($_GET["S_ProductPrice"]))?str_replace("<","%3C",str_replace(">","%3E",str_replace('"',"%22", $_GET["S_ProductPrice"]))):"") ?>" size="10" onblur="if (document.getElementById('priceRangeServerValidation')) document.getElementById('priceRangeServerValidation').style.display='none';" style="width: 114px;" />
and:
<input name="S_ProductPrice2" type="text" id="S_ProductPrice2" onblur="if (document.getElementById('priceRangeServerValidation')) document.getElementById('priceRangeServerValidation').style.display='none';" value="<?php echo((isset($_GET["S_ProductPrice2"]))?str_replace("<","%3C",str_replace(">","%3E",str_replace('"',"%22", $_GET["S_ProductPrice2"]))):"") ?>" size="10" style="width: 114px;" />