why does HDCP issue happen anyway?

for now my HDMI HDCP handshake issue has been fixed, but I am curious to know what exactly is HDCP and why does it happen anyway? is it a copyright protection sort of thing? what does HDCP mean?

HDCP is "High-bandwidth Digital Copy Protection" and it is used to provide copy protection security in digital connections such as DVI and HDMI. HDCP-compliant devices are classified as sources, displays, or repeaters (a classification that includes switches). If the source is HDCP compliant, it will not output video until it has established an HDCP "handshake" with the the devices downstream of it to make sure that you aren't somehow stealing that raw digital data in order to pirate the video.

Unfortunately, it has proven consistently difficult to implement effectively - issues like the sequence in which devices are turned on can make or break the handshake.

gonk, are all plasma's, lcd, av receivers, etc on the market today HDCP compliant? is it mandatory for a device to me HDCP comliant if it acccepts dvi or HDMI input or output?

If a device has HDMI, then it has HDCP - the HDMI spec requires it. HDCP is optional for DVI (since DVI pre-dates HDCP), so you have to check a DVI device's specs to find out if it is HDCP compliant or not. In most cases, DVI devices will include HDCP. Some DVI source components (such as OPPO Digital's 971H ) omit HDCP specifically because it allows them to operate with older DVI displays or DVI computer monitors that lack HDCP.