Seriously.
And, by the way, if you have a medical condition, don't ask random strangers about that, either-- ask a doctor.
Answer: Of course it's probably illegal. A fair use argument could theoretically be made, but I don't think there's been an actual court case over it, so I would put any such argument in the "dubious" category.
But in practice, most publishing companies don't care; in some cases they will even support your actions. The only exception is when the original text is the work in and of itself, such as with translating novels. Legal threats have been thrown around in that case, particularly in the case of American companies licensing foreign works and then threatening fan translators who had been working on translations independently (see the "Support JAST USA's official localizations of Nitro+ games!" fiasco in which many translation groups were sent takedown notices).
That's pretty much the only case in which legal threats fly around period, as such companies view fan translations as a threat to their profits, while the original company who made $movie would love for more people to buy it, regardless of the language in which it is purchased.
Copyright protects original creative expression. This is in contrast to general ideas, which cannot be protected by copyright. The difference between ideas and expression is hard to define, but a common example is that the concept of a story about two lovers torn by warring families is an idea (and thus unprotectable), whereas the particular story "Romeo and Juliet" is an expression of that idea (and thus protectable).
I think that most people would agree that the words of a movie are creative expression, and not general ideas.
What does someone else's copyright prevent you from doing? Copyright gives the author of a work four main exclusive rights: the right to make copies, to make derivative works, to distribute copies, and to publicly perform the work. If you perform an act that is within the author's exclusive rights during the term of a valid copyright, then you may infringe the copyright.
Subtitles and translations of subtitles would probably be considered derivative works, since they are derived from the original work, namely the movie.
There are also defenses to copyright infringement. Two come to my mind: fair use and the DMCA.
Fair use permits you to perform acts that would otherwise be infringements, because of certain public policy interests. It is extremely difficult to determine what constitutes fair use. Two considerations that are important factors are whether your use of the copyrighted work contributes something new to society and whether your use is taking away from a traditional revenue source of the author.
The DMCA provides a shield for website operators who accept user-provided content. If the website operator complies with certain requirements regarding taking down infringing content promptly, then the operator will be protected from many claims of copyright infringement.
Keep in mind that this is purely based on US copyright law, so things may be different if you are elsewhere in the world. Plus I am not considering the business side of things.
Whether someone read the script to you over the phone and you copied it down or you took it from the movie makes no difference.
No need to get into derived works.
It is a derivative work when you transcribe subtitles because you put in your own creative (and copyrightable!) elements into it. You choose how to represent sound effects, how to disentangle crosstalk, how to transcribe dialect, and so on.
So, if the movie creator decided to rip your subtitles off and sell them, you could actually sue the movie creator!
As a practical matter, it makes little difference. Most judges won't parse this finely, and you are equally liable whether under the copying or derivation right.
