Issue with permalinks

Hi everybody,
Yesterday, I set friendly URL in a website I’m developing. For the permalinks I took an option of the kind: http://www.myweb.com/page-example/ I also made the apropriate changes to the .htaccess file:

# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>

# END WordPress

After that, all the internal links for the different pages of the site work properly and the name of the page is shown at the browser’s bar but the problem is that after clicking on the entries page (blog), every page shows a message of “no matches found for your criteria” and you can read something of this kind at the browser’s bar: http://www.myweb.com/blog/page_id=6/
It seems like the page I click on after “blog” were searched inside “blog” despite of being an independent page.
Moreover, posts are shown like that at the browser’s bar: http://www.myweb.com/?p=50. The title of the entry is not shown.

Anybody having the same problem? Could anybody help me? Thanks in advance.