Thanks to a suggestion by Robert Gentleman, I realized that there may
be something that makes R think that mylib is a binary rather than
source package. I downloaded Brian Ripley's tree source package and
basically copied each directory. As it turns out, I have not put in a
mylib/man subdirectory (I thought I could add it any time later.) and
R was then tricked to believe that mylib is a binary! Once I add an
empty mylib/man subdirectory, things become normal with compiling
etc. Timothy, I think that your problem is likely to be the same
source then.