Michael, Alta does, has, and will ban based on IP but how far down they go in the class to mass block is unknown by me (not very wise on their part to do mass banning, already enough bad publicity from the last one). Contact your service provider about the IP info, they should have a record. If you change the number and are still having problems, I suggest getting another provider. IP changing works unless your site has spam content, duplicate content, or can be identified as a possible mirror by a percentage of similar content, similar link structure, or similar file paths. If your site is straight up and no spam, I would contact AV to lift the ban.