phpBB Search Engine Optimization

Hey there.
I have read the existent posts regarding this subject around, but none of them gave me the expected answer, so here I go.

I had a phpBB installation with Joomla once. That site was completely indexed by Google, and If I had a topic named "topic-name-here", and in that topic there was a phrase like "phrase with more words here", and I would have gone to Google and search for that phrase, Google would have found my webpage there.

Now, I started with no Joomla, a clean installation of phpBB and so. Submitted my content to Google, and tried the same "trick". It didn't work.
I do have to mention that the Googlebot is visiting my website everyday (I don't know if visiting equals crawling - all I see is the bot's IP's in the visitors list).

The question is: How do I make my posts' content being indexed by Google?
I have tried a few MOD's about it. The sitemap MOD, that's being submitted to Google for every category and forum I have and the SEO Url's MOD, with mod_rewrite that will rename the page title to a html title if the user is not logged in.

If I go to Google and type site:site-name to see my indexed pages, I can see there are only two threads indexed out of 162. And they're shown with HTML extension, meaning they've been indexed/updated AFTER the SEO MOD was installed.

Why doesn't Google index the whole forum?
The website in my Website field (Profile), if you need any other info.