laborperm,
you are totally incorrect. i believe you missed the main issue in this case.

narayanghatko_keto,
I am sorry to say that your college's international adviser is correct in this regard.

1. your OPT is granted based on the fact that you are going to complete your degree within 60 days of your filing i.e. there is a time associated with that. [ hence, post completion OPT ] since, you did not complete that requirement by default your OPT is invalidated. you are lucky that they have not caught up with your paper-work.
You can go to any school and any adviser would say the same thing.

2. because of change in the immigration policy. while you are on OPT you cannot take any classes may it be for present degree or even different degree or third degree. [ when i say OPT it is a POST DEGREE COMPLETION OPT]

there is a way you can actually work your way out of this:

1. play a "i will be deported scenario" with the Prof. ( in the course which is causing your GPA to fall below 3.0) . tell him/her you will do extra work and ask him/her to raise it by a letter grade. usually profs are helpful in this aspect. they would let you do some extra work and change the grade from (B+ to A-) this would solve your problem. and he can file a change of grade. all depends on your rapport and how you present your case to the professor.

of course you can follow your adviser's advise and get a new I-20. but you need to get that definitely. all i would say that you are lucky in this aspect that the UNIVERSITY has not separated you, yet.

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as always
what do i know (O: