if digg says that url is not valid then it will not let you submit ever because this was the same case with my blog.
as for getting indexed bookmark it on various sites.use book*marking demon for it.it is available here somewhere.
also ping on as may sites as possible not just one.
check this forum out for some high pr backlinks.
also comment on other blogs in the same niche even if they are nofollow because sometimes google also counts nofollow links.also if it doesnt count it will atleast help the se spiders to reach your blog.
gud luck with it.