Bill,
I got a variation on the pong code to work out of the box last year so I dont think the timing has changed.
FYI - my code is posted here - it doubles the number of pixels in the original pong code. Also it uses a hardware timer for vertical refresh which lets you run other code during retrace (and doesnt require disabling interrupts)
http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1231475982/0
I am not positive what the code you are starting with, but Phizone posted a couple of stripped down versions of the pong code here:
http://dailyduino.com/archives/368
This was the easiest example I found, and one of those examples should run out of the box.
All the code I have looked at had some delay code (NOPS or duplicated OUT commands) at the end of the frame write. You may need to add or remove the delay to get the sync to work.
Secondly, your TV may be picky about the video level, try an old portable TV, my Sony will go blue if the signal is too low, but the junky Phillips I use for Arduino doesnt care. Some people say that TV cards for your PC are more tolerant of wierd timing also.
Finally, double check your resistor circuit, the TV may be seeing enough signal to try to sync, but not enough to go white.