Error: Discarding duplicate request from client

[eugene at snowball.co.za]

What does this mean?
 
"Error: Discarding duplicate request from client"
 
I get this every time a session expires (Session-Timeout = 84600) every
24-hours.

For every new login I get two messages in the log file, one successful
login and the error, see log here:
 
Sun Feb  4 22:34:42 2007 : Auth: Login OK: [user.du2] (from client
highstreet port 1938 cli 00:02:6F:37:0C:07) Sun Feb  4 22:34:43 2007 :
Error: Discarding duplicate request from client highstreet:1581 - ID: 50
due to unfinished request 55156

Sun Feb  4 22:43:30 2007 : Auth: Login OK: [linx.eia] (from client
naominas port 31 cli 00:02:6F:39:E6:5B) Sun Feb  4 22:43:30 2007 :
Error: Discarding duplicate request from client naominas:1029 - ID: 83
due to unfinished request 55195

Sun Feb  4 22:43:42 2007 : Auth: Login OK: [hillhouse at dom.com] (from
client barneynas port 883 cli 00:0B:6B:09:9E:6B) Sun Feb  4 22:43:42
2007 : Error: Discarding duplicate request from client barneynas:1053 -
ID: 172 due to unfinished request 55200

Sun Feb  4 22:50:02 2007 : Auth: Login OK: [nicola at dom.com] (from client
simonnas port 2007 cli 00:0B:6B:4E:FB:16) Sun Feb  4 22:50:02 2007 :
Error: Discarding duplicate request from client simonnas:1805 - ID: 142
due to unfinished request 55240

I'm using FreeRadius Fedora Core 4, Mikrotik NAS, MySQL, and
dialup_admin.

Kind regards,
Eugene van der Merwe