It sems that, after the upgrade to OPAM 1.1, some operations such as opam search XXX fail with errors like

The package "YYY" has no version ZZZ.

where YYY is a pinned package. Not a big deal a priori since one can remove YYY, unpin it, pin it again and reinstall it (and all other packages that depend on it) — snd this for each compiler — but not fun.

I believe that the update procedure should also take more care of pinned packages.