If I turn on any encryption the laptop can not get my ThinkPad T41 type 2372-7JU to connect to the router via wireless lan. If I run as an open network, it is able to connect.
Once I enter the key it tries to connect for about a 90 seconds and then says "not connected". If I turn off encryption it connects immediately! Other laptops connect with my encryption on, no problem.
If that's a 2373-7JU, then you have a T41 with a Cisco 802.11b only wireless card. It can't do some of the latest encryption. Try to update to the latest version of drivers for the card from the Lenovo support site, and ensure the router has the latest firmware.
WEP may have the best chance of working on these earlier 802.11b models vs WPA or WPA2.
If a secure connection still cannot be made, and alternative is to deactivate the internal wireless card, and add a PCMCIA card that supports b/g/n modes.