Dell Wireless Printer Adapter 3300 - connectivity problems

Hi - it looks like I am one of many who have had issues trying to get a 3300 WP Adapter to connect to an established WiFi network.  I have read many forum articles but have not found a solution to the problem.  

I have downloaded the installation data "R147095 Dell Wireless Printer Adaptor 3300 Installation Set-UP.exe".  Saved that to a new CD and loaded it to my PC.  I get through most of the setup wizard but always fail at the same point - The adapter will not connect to the network.  All the usual checks are positive and the network key is correct and in the appropriate case.  I have run Driver Detective and that confirms that the drivers for the adapter are up to date.  The printer is not yet installed on the PC and the software for it has not been loaded.

I have tried this procedure again on a second PC where the printer had been used as a wired slave printer but have uninstalled the printer first.  Same result - Adapter fails to connect to the network.

Router is a Billion Bipac 7800 n.  I can get other "newer" devices to connect without problems but this "old" adaptor is proving stubborn.  Anybody got any ideas please (apart from slinging it) ?  Thanks