>> that sounds rather unlikely, if gcc-3.4 was installed `emerge -e system`
>> would have rebuilt it, not the 3.3 version (unless there is a dep on
>> <3.4 in system).
> 
> Does this have something to do with it?
> 
> gcc-3.4.4-r1.ebuild:
> 
> PDEPEND="|| ( app-admin/eselect-compiler sys-devel/gcc-config )
> 	x86? ( !nocxx? ( !elibc_uclibc? ( !build? ( || ( sys-libs/libstdc++-v3 =sys-devel/gcc-3.3* ) ) ) ) )"

I think so. Because gcc 3.3 is installed, portage chooses gcc 3.3
instead of libstdc++-v3.