Network Computer Inc. said it has received a $50-million infusion of capital from some of the key players in the cable industry, including Comcast, Cox Communications, General Instrument and MediaOne Ventures. The investment will be used to help strengthen the company's presence in the market for set-top boxes and digital appliances. Network Computer, brainchild of Oracle Chief Executive Larry Ellison, was started in 1996 to create a market for simple, inexpensive network-oriented computers for the corporate market. But the idea failed to catch on as prices for standard PCs plummeted. It then shifted to supplying software for set-top boxes and Internet-linked appliances such as smart phones, hand-held PCs and interactive TV. The Redwood Shores, Calif., company also announced a name change to Liberate Technologies.