When a site is banned, the backlinks to you get deleted from their database. When the ban occurred shortly before the PR update, only few links to you were registered by the bot. This would explain why it's only 3, once google slowly crawls all the other links again, PR will rise again, but don't expect 8 at the next update, this process can be pretty slow.
You are definately not banned any more, so it should just be a matter of time to get back where you were...sux because the ban probably was an automatic one, alot of huge sites (not just adult) with many subpages and pr6+ were banned lately, many totally unjustified...maybe some bug
