Ever found a URL ending with ".0″ (that's 'dot zero') when searching for an item in Google? You probably haven't, because it's impossible to get a URL that ends with ".0″ listed in the Google search-result pages.
Here's something to try: search for "Windows 1.0″ in Google, and in Yahoo. While Yahoo will show a result from Wikipedia, with the following URL "http://en.wikipedia.org/wiki/Windows_1.0", Google will not. And it's not because the page isn't popular, or because no one links to it (1200 inbound links). It's merely because Google can't, or won't, index those URLs ending with .0 .
This can pose some problems for websites who wish to publish software (think versions as 1.0, 2.0, ...), or other articles relating to "x.0″. It's easily resolved by changing the URL of course, but for automatic software which creates URLS (think WordPress, Yoomla), it's a hard thing to do.
Solutions are rewriting the URL, or making sure the same page with an added "/" works too (so you'd make "mysite.com/blabla_1.0″ also accessible at "mysite.com/blabla_1.0/"). I'll bet it can take a while to find out why your pages aren't listed in Google, despite your best SEO efforts!