I recently had a problem with a Drupal site where I chnaged the ownership of a page from the main administrative user to another user on the site. I basically wanted to give that the user the ability to edit that specific page's content.

The problem arose when I logged in as that user and went to the page, the "Edit" tab didn't appear.

I went into the admin area and verified I had the permissions set correctly, and everything seemed fine. I even logged out and back in again as the user in question, but still no "Edit" tab.

After Googling the issue (as I always do), I found the problem. I had the input format of the page inquestion set to "Full HTML", but the user didn't have the permission to use that input format, so Drupal refused to let them edit it.

So I logged in and changed the normal input format to include a few more tags the user would need, saved the page, and voila! The user could then edit the page!

I hope this helps another Drupaler down the road.