AV appears to be examining ways of getting rid of the spam, doorway pages and so on, resulting in some domains being blocked. There is a response on their message boards here explaining what is potentially bannable.
If a submission gets the 'too many urls submitted today' message then they may have caught up with the site.
Well, lately I have noticed that after you submit, it takes about a month or two for them to spider your entire site. About 2-3 weeks after that it will appear in their canadian index (at least mine did) and 1-3 weeks after that it should appear in their general index.