I'm assuming you're talking about TCP ISN's, and the article you read was by Ankit Fadia?

As far as I can tell from the tcp specification, the ISN doesn't have to be set to 1 at bootstrap time to meet standards, but to answer your question directly if it IS set to one at bootstrap, then yes once a machine is restarted the ISN would be 1 again. This is all layed out in the rfc793 (TCP): http://rfc.sunsite.dk/rfc/rfc793.html

for more information on how more secure implementations SHOULD generate/permute ISN's check out steven bellovins RFC on ISN's: http://rfc.sunsite.dk/rfc/rfc1948.html

also, for info on how most implementations actually do their isn generation/permutations (which is poorly for the most part) read Michael Zalewski's research here: http://lcamtuf.coredump.cx/oldtcp/tcpseq.html#abs and here: http://lcamtuf.coredump.cx/newtcp/

-Ryan