You just bought a Blu-ray Disc Player and connected it to your older HDTV with a HDMI cable. When you tried playing a Blu-ray disc a HDCP error was shown on the screen. The movie wouldn't play.
This is a known issue with HDCP, and it's one of the biggest hassles consumers will have to deal with when utilizing a HDMI cable on their HDTV. You will get a HDCP error if you try watching HDCP encoded content when using a HDMI cable.
The problem is that if HDCP exists anywhere in the video stream then all devices and cables accessing this content must be HDCP compliant. If one device or cable isn't HDCP compliant then you get a HDCP error.The only solution is to either replace the HDMI cable with a non-digital cable or replace the HDCP-less device. This could mean buying a new HDTV.
In fact, I worked with a reader last year troubleshooting a HDCP error on his TV. What happened is that he bought a Blu-ray Disc Player and connected everything properly only to get a HDCP error. After a few emails back and forth we discovered that his HDTV wasn't HDCP compatible, which is why he got the HDCP error.
The reader ended up buying a newer HDTV with HDCP, and his Blu-ray Disc Player worked perfectly with HDMI cables.