I have an Insignia 27" CRT from Best Buy. Just got Comcast cable, and maybe they're using a different remote now. I tried sooo many codes, and decided to try a 1 in front of the 4-digit code. What FINALLY worked for me is a five-digit code - 10463

I even downloaded the online user manual for that remote from Comcast, and all of the codes were 4-digit, but apparently it's a new model that takes 5-digit codes now.
Thanks to the community for sending me in the right direction with the 0463..