Is it a passive cable (consisting of just wires and connectors) or an active cable which includes HDMI amplifiers? Monoprice's Redmere cables are active. Active cables are directional.
If you have a passive cable, I think it's likely that it has an intermittent connection. Stress on one end or the other would cause it to no longer pass a signal. A broken wire in the middle of the cable is another possibility. It'd make intermittent contact depending on how the cable is bent.