VPN and proxy is hard to trace by its very nature, and with the amount of hackers and cyber-criminals causing all sorts of chaos like what happened to the credit company, many sites, isp's etc are seriously trying to cut down on VPN/proxy traffic by unregistered users. With as available as personal IP's are, there's no real need for sharing accounts, which most isp's don't like in the first place as it cuts down on account incomes, and increases bandwidth traffic.
So it's not surprising you are running into blocked sites, service issues etc.