That is a weird one.  Java serialization can sometimes be tricky.  I  
think the issue is that you have a serializable object which doesn't  
have a default (no-argument) constructor or is subclassing from a  
class with the same.  See:

	http://forums.sun.com/thread.jspa?threadID=686452

Sean

On Dec 5, 2009, at 5:52 AM, John Smith wrote:

> When restoring a checkpoint, I receive a strange error:
>
> STARTUP ERROR:
> An exception was generated upon starting up from a checkpoint.
>
> java.io.InvalidClassException: brain.BrainHelper; brain.BrainHelper;  
> no
> valid constructor
>
> This class BrainHelper is only used as a helper class to evaluate the
> individual, and is not referenced by EvolutionState, the problem, or  
> the
> Individual. I could create a default constructor that does nothing,  
> but I am
> curious why this class is even relevant?
>
> Thanks for any help.