The examples given about the Unix team are clearly singular in meaning.
The Allyn & Bacon Handbook which has been widely used in U.S. colleges for years states that "Collective nouns have plural or a singular sense depending on the meaning of a sentence."
The AB Handbook attempts to clarify its opinion by stating that when a noun (such as audience, band, bunch, committee, crew, crowd, faculty, family, group, team, staff, tribe, etc.) "refers to individuals and their separate actions within a group, the sense of the noun is plural and the noun takes a plural verb."
Thus, to say that "The support team
have different opinions about what the
problem is" would not be incorrect.
It is clear to me, however, that there is a difference in sensibility about this between British and American speakers, with British speakers being far more likely to say the "The team are going home" than a typical American, even though the meaning is exactly the same.