Drifter Bro, here is what I have understood in this case. You need to be employed in the field of your study within 90 days after your OPT starts. However, if you are not able to find a subject related job within 90 days then your OPT gets canceled and then you have a grace period of 60 days to either join a school or to leave the country. If you are not able to fulfill either of those two requirements within the 60 day grace period then you become out of status. However, of you use your grace period before your OPT starts like I did, then you have to get a job within 90 days or get another I-20 within 90days. Hope this makes things clearer to you now. Got more questions? Shoot over here. I will answer if I can. And lastly, for the very worst case scenario, what you can do is you can do a volunteer work in your subject related area to maintain your OPT. That is what my international advisor told me. :-)

Sparrow