The C7000 can only see one device at a time, but you can switch between computers.
When you're in Media Play and you press the RED ( A ) button, it will display a list of devices. As long as you have a DLNA server that has accepted the TV on the network, you can select it. The key is to make sure all of the computers have accepted the TV on the network, and then choose the one you want to work with.
My UN5C7000 will DNLA connect with only one of my three PCs on the home network using WMP11. On all three PCs, WMP11 sees and has been enabled to share with the TV. Can the C7000 only see one DNLA device at a time? I've tried only having one of the other PCs on when I turn on the TV, but nothing seems to work. Any suggestions?