select="//tr[@valign='top']/td[@class='class1']/td/a/br/small/b/../../../../..
There are two td elements in this path. I don't believe your source document has a td element that is a child of another td.
Also, don't go all the way down and then up again. Use predicates like
//tr[@valign='top'][td[...]/a/br/small/b]
which will select a tr element that has the relevant tree beneath it.
Michael Kay
http://www.saxonica.com/
Author, XSLT Programmer's Reference and XPath 2.0 Programmer's Reference