Is that router capable of wpa-enterprise with TKIP? I guess you imply you had connected wirelessly before. For that level of security I thought you needed a RADIUS server or hosted RADIUS service like Witopia's,
www.witopia.net to run that level of security. I thought the asus only does WEP. You may want to check the security capabilities of the adapter itself to make sure they match up with your router setting. I'd also make sure you don't have MAC-address filtering turned on. It doesn't really work anyways and may be blocking the new device.