The message "[t]he restriction is due to a substantial link having been discovered between your account and another account with a history of abuse activity" is not (necessarily) due to connecting through a proxy or VPN; it means that the system (or the staff) has good reason to believe that the account belongs to someone who has been suspended for abuse in the past. If that turns out to be the case, you probably won't be allowed to keep a hosting account active. (Note: I have no way of checking things myself, and there wont be any public discussion of the techniques used to determine "substantial links", since that would be tantamount to telling people how to get around the system. A staff member may review the problem and resolve it in your favour if it's an obvious mistake, but there's little room for "benefit of the doubt" with current plans to open up hosting worldwide and the abuse potential that brings.)