By default, the Palm TX only supports WiFi connections using WEP or WPA security. However, support for the more modern WPA2 was added post-release in an update known as the Enterprise Security Upgrade. This update can be installed via an SD card in combination with an installer app on your TX, both provided in the package below.
Note that this upgrade adds support for WPA2 Enterprise, not WPA2 Personal. In order to connect to WiFi, your router must support the former protocol. Your router must also accept legacy 802.11b WiFi connections, as this is the highest standard supported by the Palm TX.