I just grabbed the latest CVS version of ruby-mode.el last week, and it 
seems to have some nice new fontification and indentation features.

However, once I have loaded a ruby file, if I then load a C++ file, any 
single line comments (using //) now are not fontified right.

Is ruby-mode changing some global fontification resources?  If I never 
invoke ruby-mode, then the C++ code looks fine...

Has anyone else seen this?

BTW, I am using emacs 21.1.1 on Linux.

-- 
The key of strategy... is not to choose a path that leads to victory, but 
to choose so that all paths lead to a victory.
-- L.M. Bujold