The receivers are generally using DHCP to get an IP address on the network. (automatically assigned IP addresses). The DHCP assignments are "leases" from the DHCP server (usually your router) and they can expire. If you reset the machine and it works, it could be that the IP lease had expired and by rebooting the receiver it picked up a new address and joined the network.
If you know how to add things to your network, you might try setting the receiver's IP address manually. Manually set IP addresses don't expire. This has solved the disconnect/reset issue for several people.