Help - is this a JDBC issue??

I'm working on a web application and everything was fine until this morning when I modified some Java code copied it over ran the application and got this:

Error: 500
Location: /nzfm_frame.htm
Internal Servlet Error:
java.lang.IllegalStateException: Can't happen - classname is null, who added this ?
at org.apache.tomcat.core.ServletWrapper.loadServlet(ServletWrapper.java:261)
at org.apache.tomcat.core.ServletWrapper.init(ServletWrapper.java:289)
at org.apache.tomcat.core.Handler.service(Handler.java:254)
at org.apache.tomcat.core.ServletWrapper.service(ServletWrapper.java:372)
at org.apache.tomcat.core.ContextManager.internalService(ContextManager.java:812)
at org.apache.tomcat.core.ContextManager.service(ContextManager.java:758)
at org.apache.tomcat.service.http.HttpConnectionHandler.processConnection(HttpConnectionHandler.java:213)
at org.apache.tomcat.service.TcpWorkerThread.runIt(PoolTcpEndpoint.java:416)
at org.apache.tomcat.util.ThreadPool$ControlRunnable.run(ThreadPool.java:501)
at java.lang.Thread.run(Thread.java:484)

Now I can't get to any pages not even the index page, I have taken the code out that I added to check if it was causing that (didn't think it could be) all I get is this above error. Is this to do with the JDBC driver or Tomcat?

taupo=> select version();
version
---------------------------------------------------------------
PostgreSQL 7.1.3 on i686-pc-linux-gnu, compiled by GCC 2.95.3

JDBC Driver:
jdbc7.1-1.2

The application code is pretty much all written on the JSP pages and I am refactoring the code for a model view controller architecture, only just started the refactoring, nothing that could be causing this I'm sure. The code I had been adding this morning just manipulated string formatting.

Advice please! The system is supposed to be in a state that the users can have a preview of it tomorrow!

Regards,

Sharon Cowling