Just to confirm: you get no exception when you load the DLL, you get
the exception when you attempt to invoke one of the methods?

If that's the case, then the JVM is unable to find the methods it
expects to find in the DLL.

Note that the DLL was necessarily written to be used from a particular
Java class. That class declares a number of native methods, and the
DLL contains implementations of those methods. You cannot load the
same DLL from another class and expect to be able to use those methods
as though they belonged to the new class, because the method names in
the DLL are determined (in part) by the name of the class they belong
to.

Did you rename the class the dll was intended to be used from? Did you
change its package declaration?

If any of this is unclear to you, then post some real code (not just
an abstract example).

/gordon