problem after installation

[Guest]

I?ve installed the packge (free version).

When I browse at http://localhost/osCommerce there?s no problem.

But when I click in any link, appears this error:

 

Fatal error: Unknown(): The script tried to execute a method or access a property of an incomplete object. Please ensure that the class definition <b>navigationhistory</b> of the object you are trying to operate on was loaded _before_ the session was started in c:inetpubwwwrootosCommerceincludesapplication_top.php on line 309

 

what?s the problem ?

OS is Windows 2000 prof.

I?m using IIS, but the error appears using Apache too.

 

Thanks