PLS-00907 strange situation

When compiling several packages I got in one of them the PLS-00907 (cannot load library unit) error.

Error: PLS-907
Text: cannot load library unit %s1 (referenced by %s2) 
------------------------------------------------------------------------
---
Cause: PL/SQL is unable to find and load a library unit that was
        previously available.  This typically happens when you try to
        load a unit which references another library unit that is
        non-existent or invalid.
Action: Provide the needed library unit.

 The problem was that the package referenced (in the %s1 place) existed, was valid and was also referenced by other packages that were valid.

After some tries dropping and replacing the referenced package with no success I look more carefully and the %s2 was not the package were the compilation error occurred, but another that was valid. So I recompile that package and presto! it worked the original package compiled now correctly.

Using Oracle 11.2.0.1.0