Copying programs

I've always been able to copy programs from my DVR to a DVD with my DVD recorder.  Then a few months ago I could only copy some programs. Now recently I can't copy any programs from my DVR.  It just says "Copy-protected, cannot record".  Where is this coming from?  My DVD recorder? My DVR?  The networks?  Is there any solution to this problem?

Please advise.  Thanks.