Greetings Reader

At home I tried to secure my wireless network through the router’s wireless interface with the following security settings:
Network Authentication Type: WPA-PSK
Data Encryption Type: TKIP
I also changed the SSID and changed the default WPA Pre-Shared Key.

These settings worked perfectly fine about 2 months ago when I was still using Windows XP Professional. Currently I am running Windows Vista Enterprise (Build 6000) that I installed clean after formatting. My issue is the following: I am only able to connect and have wireless Internet access with my HP Pavilion zd8000 with a Broadcom 802.11g Network Adapter with the open system or shared key authentication settings (thus unsecured). When I set the above mentioned security settings within the router menu I cannot gain access to the secured network because of an error message from Windows saying that the network key or passphrase does not match the key from the wireless network even though I am 100% certain the key has been entered correctly from the key that was set within the router menu.
This strikes me as extremely odd and I am unable to identify what causes this issue. I already upgraded the firmware from version 1.9.5.4 to 1.9.5.6 and restored all factory settings before trying again with no change.
Can anyone help me out here?

Thanks in advance!