web client session not available

Dell 760 computer with xp pro SP3, IE8 has issue with sirsi staff web client drops connection after 10 minutes with error: ” Web client session not available” . I have Dell 755’s that have no issue. I have put wireshark on the network and found nothing. The NIC was set down to 10 mb, Power managment is set to always on and no hybernation. XP is updated, flash is 10.1.53, Java at 1.6.21. I am out of things to try.
Thanks libtech