In the definition:
<bean:define id="currAccount" scope="session" type="java.lang.String" value="<%
= (String) session.getAttribute(Tags.CURRENTACCOUNT) %>" />
if type is not entered, the default ends up trying (and failing) to be
com.netscape.jsp.JSPTree currAccount = null;
in the java file generated by the JSP.
Casting resolves the problem.