A few thoughts;
I have experienced the same problem with my XPS 8500. My video card is the nVidia GT640 and use my Philips HDTV for monitor. I sent a round of queries to Dell and Philips but received no replies.
The fix:
1) Downloaded the latest updates for the HDTV, one of which even specified 'the HDCP' issue. BUT I already had that installed. However a re-install was done and the problem vanished.
2) Only to reappear after a reboot, the next time I attempted to watch a Blu-ray movie! Rats!
The HDCP seems a protocol to avoid copying movies from PC to another device. Since my HDTV has several HDMI ports in use: Cable TV feed, Blu-ray player and XPS 8500. A radical thought occurred:
With everything still turned on I found a fix':
1) Unplugged the HDMI: PC to HDTV cable from the HDTV.
2) Counted to 10
3) Plugged the HDMI cable back in.....
BINGO! the HDCP error message vanished, the Blu-ray movie played just fine. I know this is not a real fix, but it works.
Please let me know if my solution works for you?
Thanks!