recommend it) or by disabling the ipv6 modules in /etc/modules.conf or /etc/modprobe.conf (can't remember which is the correct file for 2.6, probably modprobe).
If you don't allow the module to load then obviously the kernel is not-ipv6 enabled and nothing else will work (all scripts/programs and the like determine they're running in a non-ipv6 environment and gracefully fail or go back to default ipv4).
Yes. Try this:
alias net-pf-10 off
in /etc/modprobe.conf