does anyone else ever had this problem/issue? when i change from an hd source to a sd source on my cable box the picture flickers a bit and goes black/green for a second and sometimes the tv beeps.

the tv is hooked up via hdmi could the cable be faulty? when i hooked up the cable box via component this didn't happen.

Nothing to do with the cable. It's most likely a cable stb issue if once the HD material is displayed all is ok until you switch to SD and back.

larry