I presume you have also seen this thread?
[Link: remotecentral.com]Do you have latest firmware on your router?
Can you make all this work if you disable WEP?
Does it work properly if you reconfigure RFX to not be inside DHCP IP address range on the router?
Does it work with WEP if you use Hex Key vs Passphrase?
For me, Extender Discovery only works as follows:
1. PC is wired to Router.
2. RFX is wired to Router.
3. PC is running Extender Discovery
4. Switch on RFX switched from Position 1 to Position 3.
5. After about 30 seconds, Extender Discovery sees the RFX.
Have you also reviewed this thread?