I've gotten three different errors on four different runs, all of which
involve generating the RI documentation (one of the errors has already
scrolled past the end of my terminal buffer, so I can't copy-and-paste
it):

Generating RI...
/home/pbrannan/download/ruby/ruby/lib/rdoc/ri/ri_writer.rb:59:in `path_to_dir':
+cannot convert Object into Array (TypeError)
        from /home/pbrannan/download/ruby/ruby/lib/rdoc/ri/ri_writer.rb:42:in
+`add_method'

Generating RI...
/home/pbrannan/download/ruby/ruby/lib/rdoc/markup/simple_markup/fragments.rb:146:
+[BUG] Segmentation fault
ruby 1.9.0 (2004-09-29) [i686-linux]

Are these known problems?  Are there any known workarounds, other than
trying over and over until it succeeds?

Paul