Erroneous output from ri File

I mentioned this in another thread, but didn’t get an answer.

For me, under 1.9.1p429 (RubyInstaller) under Windows, ri File says only
this:

(begin)
------------------------------------------------------- Class: File < IO
[no description]

Class methods:

binread

(end)

ri IO shows:
(begin)
More than one method matched your request. You can refine your
search by asking for information on one of:

TkItemConfigMethod::IGNORE_UNKNOWN_CONFIGURE_OPTION [gem
tk_as_gem-0.1.0]
TkItemConfigMethod::set_IGNORE_UNKNOWN_CONFIGURE_OPTION! [gem
tk_as_gem-0.1.0]
(end)

Is something missing from my Ruby installation?