Well, actually, you was alread adviced about some working methods of solving your issue (both right and wrong ones, but it is anyway your decision to take ones to use), so I'll just clarify the simple thing:
You can suffer on such problems in relation to IPv6 **ONLY** in the case when your ISP **DO** have IPv6 support (say, announce IPv6 preffix to you via SLAAC or DHCPv6), but having **BROKEN** IPv6 routing. (well, it can also be the case that they had no VLAN per customer and you're getting foreign SLAAC/DHCPv6 announces from some of your neighbours, but I'd prefer to not think such a worse things about ISP I don't know yet :D) So, ideally, you **SHOULD NOT** disable IPv6 on your side, but shame your ISP support line (for either broken IPv6 routing or not having VLAN per customer, depends on the real case) instead. P.S. don't consider "capsed" words as crying, please. Just consider it as "extra bold" mark.
