I had submitted around 25 links but google webmaster tools shows only 20 have been indexed so far and the remaining 5 links never get indexed.
Check the crawl rate you have set for the Google bot. I wonder if you increase the frequency if that would help your remaining five links to get indexed. Another idea is to make sure those links are valid and don't produce an error because of redirection or any other restrictions. In your sitemap file maybe you can change the date for last update to a more recent timestamp. Curious to know what happens.