Alas! they had been friends in youth but whispering tongues can poison truth.

Old friendships rarely end in one blow. More often, something is said about one person to the other, repeated a little differently each time, until what either believes about the other no longer matches what actually happened. Rumour works slowly, and by the time the damage shows, the original story is hard to recover.

If a long friendship has cooled on the strength of something you heard rather than something you saw, consider going to the source. Ask your friend directly. The conversation may be awkward, but it is much less costly than losing years of closeness to a version of events neither of you wrote.