Until I get more info about the project it is difficult to decipher the exception. To me, it sounds like a JSTL version problem. About halfway through the exception, it was trying parse through a directive that it could not understand. The big indication is the "JasperException". I ran into similar problems in my JSP. I notices that you are using the latest version to Tomcat which uses JSP 2.0, JSTL1.1 and Servlet 2.4. And when you went to JBoss 3.2.5, the exception got resolved.
From my inference, I would say that you were using JSTL 1.0 and when you moved to JBoss 3.2.5(JBoss 3.2.3 was using Tomcat 4.x) with Tomcat 4.x which uses Servlet 2.3
Here is the breakdown: JSTL 1.1 requires Servlet 2.4 JSTL 1.0 requires Servlet 2.3 And little 1st 2 line changes in the web.xml
subject: Mystery Exception: Failed to load or instantiate TagLibraryValidator class