[LukeShu]

The two meanings you present are the same meaning. It could roughly be "all except" in either case.

    > (where it means "almost" -- e.g., "He all but went bankrupt)

This makes sense with the individual words. On the scale of loosing money, he did everything up to, but not including, going bankrupt. He did everything except going bankrupt; which is almost going bankrupt.

I see your point that because in a non-quantitative description, it effectively means "almost", people might confusedly use it to mean "almost" in quantitative descriptions, without thinking about what it means.

    > Actually, the problem is ...

So, I cede that that is a problem, but I don't agree with the "actually." There are people who don't realize that it means "almost", and might say "He all but went bankrupt" to mean that he really went bankrupt.