page.php doesn′t work

Recently I experimented a really weird bug, every time I try to view a page doesn′t shows the page.php template use index.php, I thought could be some functions.php hacks I′m using (typical ones, login logo, remove dashboard widgets, etc) but even if I erase functions.php file the problem persist.

So, to check what happend I insert a function on the header.php of the theme to see how it WP looks the content. The function I call is if_page located in wp-includes/themes.php.
This is the answer if I get into a custom post type url:

string(4) "home"
bool(false)
string(6) "single"
bool(true)
string(8) "category"
bool(false)
string(4) "page"
bool(false)
string(3) "tag"
bool(false)

and this is the result of get into a page url:

string(4) "home"
bool(true)
string(6) "single"
bool(false)
string(8) "category"
bool(false)
string(4) "page"
bool(false)
string(3) "tag"
bool(false)

It should show true on page but wont.

Any idea? I′m totally clueless :S ??

Thanx.