R2.10 vs OSX 10.4.11

Hi,
Can someone let me know what should work and what is known not to work 
with the latest R2.10x when installed on Tiger (10.4.11)?  I did a quick 
tryout and found that the ? command brings up a blank help window.  The 
help.start() (I think that's the command) brings up a R-help window in 
my web browser, but only some items' help pages show up there.

I'm happy to do some testing or debug work, but just don't want to beat 
myself up against known walls.

To answer the obvious:  I'm lucky still to have a Mac at work at all, so 
the chances of IT getting me a Leopard upgrade disc are zero or less.

thanks
Carl