Problems with C54RU in Windows XP.

Taken from Conceptronic's FAQ about C54RU:

The problem of disconnection due to limited or no connectivity occurs when the unit does not have a correct IP address assigned.

Be sure that the option “Use Windows to manage my wireless network configuration” is disabled.
This can be found in the 'Wireless tab' of the wireless network card properties of the wireless card.

If this box is not disabled, Windows will manage the wireless connection.
You are not able to use the wireless utility of the Conceptronic product.

Additional:
Be sure that the option “Enable IP setting and Proxy setting in profile” in the 'Option tab' of the wireless utility is enabled.
Be sure that there is a working DHCP server or other device is acting as an DCHP server available in your network.