Are you suggesting that the receiver(s) and the server should be connected to the 10mbps hub?

No, only the specific device that's giving you trouble. In this case, the Receiver.

I don't understand why putting a 10mbps hub between the receivers and the 100mbps DHCP (router) would make any difference as the DHCP isn't going to respond any faster.

Because if it's the problem Roger thinks is happening, it isn't happening at the DHCP level. It's at the hardware level, during the initial ethernet handshake between the hub and the device. Inserting a piece of relatively dumb 10mbps-fixed hardware at that point often solves the problem.