Page not found in drupal 7
Check if anything in this list of typical things might help:


Make sure "clean urls" is enabled. Refer to "Clean URL leads to duplicate URL after migration to another hosting" for more details on that.
Make sure the value of "base_url" is set correctly (in your settings.php).


Another option is to check the logs. If you find errors there (like PHP Fatal errors), then try to narrow down that error to the module that causes the error and disable that module (and report it in its issue queue on Drupal.org). If you don't know which module is causing it, then first disable all modules, and enable them one by one again. If at some point the error then comes back, then that must be the problem module causing your problem. Then disable that module again and re-enable all others.