Firstly, no need to repeat the same nameserver address three times - I should have been more clear in my example that they were three different addresses. That shouldn't harm, though.

I suspect that you forgot to make the script executable. Either make it executable (chmod +x /usr/local/bin/timesync.sh) or explicitly start a shell to interpret it:

;@AC ;@EXEC /bin/sh /usr/local/bin/timesync.sh 208.14.208.19 208.14.208.19 208.14.208.19

Also, check for errors on the console. I would hope that Hijack would print something if exec() fails! If you don't see a line beginning with "hijack_exec(" then it's not even trying. What I get in my boot log is something like

Starting player
Hijack: intercepting config.ini

hijack_exec("/usr/local/bin/timesync.sh 10.70.x.a 10.70.x.b 10.70.x.c 1)
player.cpp : 385:empeg-car 2.00 2003/04/01.
Prolux 4 empeg car - 2.1434 Mar 26 2003
Vcb: 0x40891000
30 Jul 19:09:35 ntpdate[72]: adjust time server 10.70.x.a offset -0.391570 sec

There's (unsurprisingly) a ten-second delay during this phase.