java.lang.NullPointerException

Hi:
On my localhost I use ie4, jdk1.2.1,jsdk2_1-win, JigSaw2.0.2, JdbcOdbcDriver and MSAccess
as a 'pilot plant' setup. Mostly everything is running quite well.

But not always...e.g. 

Servlet1 contains a conventional registration form (name, email, address et cetera)
On Submit I go to Servlet2 
(where the registration of submitted values in a db table is intended to occur) 

However I get 
"Servlet has thrown exception:java.lang.NullPointerException:"

WHY?

-dan