According to a tenth century halachic text, Baal Halachot Gedolot, the eighth of Tevet (this coming Friday) will mark the anniversary of the translation of Torah into Greek. The translation is alleged to have happened in the third century BCE, more than a century before the events of Chanukah.
We know little about how this translation came about; we have several different traditions regarding who did the translation, how, and for what purpose. We don't know whether the original translation was the Greek Septuagint, although this work is often granted that pedigree. We do know that traditional Jewish texts label the translation a tragedy, but we don't know why.
An early Jewish source, Masechet Sofrim (1:7-8), compared the translation of Torah into Greek with the worst event in our nation's religious history. As the text tells it, "Once five elders wrote the Torah in Greek for King Ptolemy, and that day was as harsh for Israel as the day the Calf was created, because the Torah could not be properly translated. Another time, King Ptolemy gathered 72 elders and put them in 72 houses without revealing why he had gathered them. He went to each one and told them, 'Write the Torah of Moshe, your master, for me.' G-d placed counsel into each one's heart, and each of them wrote an independent Torah. They changed thirteen things: 'Elokim created in the beginning'…" According to the first part of this account, Greek itself is inadequate to translate the Torah, and the disaster of translation was that it necessarily betrayed the original. Of course, omnis traductor traditor - every translator is a traitor – but this passage contends that Torah is uniquely beyond translation. [Of course, later religions made the same claim regarding their sacred texts.]
The explanation found in Masechet Sofrim is difficult, though, in light of a passage in Talmud Yerushalmi (Megilah 1:9), "Rabban Shimon ben Gamliel said: Tanach may only be recorded in Greek; the sages checked and found that the Torah can be translated properly only in Greek." Based on this text, what was the danger in translating Torah? Why was it considered catastrophic?
One approach is found in a midrash (Tanchuma Vayera 6): " R' Yehudah haLevi b'R' Shalom said: Moshe requested that mishnah be put in writing as well [as the written Torah], but G-d saw that the nations would translate the Torah and read it in Greek and say, 'We are Israel, too.'" In other words, the problem of translation is not in its inadequacy; rather, it is in its authenticity. Once the Torah is available in other tongues, the Jewish nation loses its special character, as anyone can mimic it and claim the heritage of Torah for themselves.