Airport Utility doesn't detect Airport Express

Hi,

I have 3 Airport Express' which I use to join my existing wireless network and stream music via airtunes. Everything has been working fine until recently when I upgraded my wireless router to a Belkin Play N600.

The router is set up and connected to the internet, and my Airport Express' also connect to the network fine (they are shown as connected when you access the router). The Airports connect fine both wirelessly or via ethernet. However, despite the PC also being connected to the network (again shown as connected to the router and listed next to the airport express') the airport utility does not see the airports when you do a scan?

What is even stranger is if go to "file->configuration other" on the airport utility and then type in the airports IP address and password you can access the Airport and change settings etc. It just doesnt recognise them when you do a scan (and therefore it doesnt detect them in iTunes either)?

Any help anyone can provide would be greatly appreciated!

Thanks in advance

Paul