Wi-Fi integrated vs USB adapter

I have a situation where the Intel Wireless Pro 4965 integrated adapter on a Toshiba Prestige P200 does not appear to work while a NetGear WG111 USB adapter on the same laptop works without a hitch.

The environment : we hooked up a new Zyxel wireless router to an already operational Terayon router with ADSL access through a TV cable. The idea was to use the Zyxel simply as an access point for 2 or 3 wireless laptops. We prepared the Zyxel appropriately : deactivation of DHCP server function, change of IP address from 192.168.1.1 to 192.168.1.39 (to avoid overlapping with Terayon) and cable link of the Zyxel to the Terayon through the LAN hubs. We left our network unprotected at this stage.

Cable connection test : two pc’s were cable connected to the Zyxel and worked fine. We learned from the ISP that the way they work is to clobber the original IP addresses : their system changed Zyxel’s address to 85.218.34.1 and the first pc’s to 85.218.35.81. Anyway, we made no change ourselves and everything worked as soon as we connected the cables.

Wireless connection test (Intel) : Although the Intel Wireless Pro 4965 integrated adapter on the Toshiba worked fine in another location where there was a unique Zyxel wireless router for ADSL operations, we were unable to connect in the environment described above. The physical on/off switch on the laptop was properly set. The Connectivity Doctor Utility showed clearly that there was a connection problem and nothing wrong with the integrated adapter. The SSID of our own network did not appear among the networks available in the building.

Wireless connection test (NetGear): When we connected the NetGear WG111 USB adapter, our SSID appeared among the networks available and we connected successfully.