[tex-live] ??? cannot be found in...

[Karl Berry]

    chemscheme cannot be found in
    http://mirror.ctan.org/systems/texlive/tlnet/2008

As Robin implied, it seems you got an old tlpdb somehow.  Those packages
have not existed for quite a while, so it's correct that the mirror does
not have them.

What's useful information in failed download reports is the actual
mirror that was used; "mirror.ctan.org" multiplexes among all
(supposedly) up-to-date mirrors, so it doesn't tell us anything about
which host might actually have the stale data.  tlmgr should tell you
what individually mirror actually got chosen, I think/hope ...

k