Dreamcast Internal VGA incompatible with my TV

This is my first post, but I've done some searching already so I figure I'd ask here.
I followed RedDragunee's tutorial for the internal VGA mod and it works beautifully on my 21'' monitor, but when i try to play on my 32'' HDTV, all i get is a "Not Support" message.
What vga signal does the dreamcast output? The specs on my TV manufacturer's site says my TV supports as low as 640 x 480.
Any ideas would be appreciated.

Thanks,
Vonn

edit:
my tv's specs: http://www.sceptre.com/Products/LEDTV/Specs/E325BV-HD/E325BV-HD Mainpage.htm

 

Dreamcast outputs 640x480 resolution. Either your TV has to be manually set to support 480p or perhaps something went wrong with the internal mod??? I'm not entirely sure...

 

Maybe it expects sync on green or so. What model is your HDTV?

 

Right there in the link in the edit, it's a E325BV-HD. If you go to the specification tab there it says it accepts VGA signal down to 640x480

Edit:
Hurricane Sandy knocked my power out for a while, but when it's up i'll test my TV with a computer down at 640x480 to see if it's the vga mod or the TV itself that's wonky.