The thing with vcc and adwords vouchers does not work as easy as explained in the threads here... this was working several months ago... i have tested a lot these days, and google changed a lot of things. If i get time, i ll probably post a detailed thread about it... if not... keep in mind that google freeze accounts created with vcc coming from major vcc providers... (although the account looks active, you ll be delivered no impressions, no matter how much you bid).
So , yeah, you need different ips, domains, cookies, vouchers link (you can t use the same one) and a vcc provider that is not flagged by google/