Date index for Jun 2002

I've installed Achievo. Don't know if I've done it correct but the 
following message keep appearing.

Warning: open(/tmp\sess_22a61bffada1208843753014b4d6f0ac, O_RDWR) failed: 
No such file or directory (2) in 
c:\apache\apache\htdocs\achievo\atk\session\class.atksessionmanager.inc on 
line 14

Warning: Cannot add header information - headers already sent by (output 
started at 
c:\apache\apache\htdocs\achievo\atk\session\class.atksessionmanager.inc:14) 
in 
c:\apache\apache\htdocs\achievo\atk\security\class.atksecuritymanager.inc 
on line 279

Warning: Cannot add header information - headers already sent by (output 
started at 
c:\apache\apache\htdocs\achievo\atk\session\class.atksessionmanager.inc:14) 
in 
c:\apache\apache\htdocs\achievo\atk\security\class.atksecuritymanager.inc 
on line 281
Inloggen mislukt

Warning: open(/tmp\sess_22a61bffada1208843753014b4d6f0ac, O_RDWR) failed: 
No such file or directory (2) in Unknown on line 0

Warning: Failed to write session data (files). Please verify that the 
current setting of session.save_path is correct (/tmp) in Unknown on line 0

The error line seems to be referring to :
  session_start();
  session_register("g_sessionData");

but I can't find those functions anywhere in the code.
I'm I missing something or just my brain.

Kind Regards
Eddy van 't Westende