Battle CTDs are sometimes caused by insufficient video memory
or by a unit missing skins
or by having the graphics detail up too high.
I think the current RC/RR compo is very memory hungry - I found I could only play for an hour on my 1GB RAM system before it crashed.
the newer skins for some units seem to use a lot more memory too.
(I suspect there's a limit to the RAM the game engine can address?)