I am experiencing an issue trying to edit pages that sounds very similar if not the same as Michelle is trying to relate.
When I login to my development portal and navigate to a page I wish to edit, I ensure the radio button is set to Edit, and that the "Design" icon has a minus sign on it. I can click "Edit Text" and see the text editor and make changes there. However when I click "Update" or "Preview" to save the changes, the page just reverts to its previous state and the only thing that happens is the "View / Edit" radio button toggles to the "View" state. Because of this I am unable to edit my pages.
I have tried logging out and back in, restarting IIS, restarting DNN, checking file permissions, logging in from other computers, and all kinds of clicking to get SOMETHING to work. When my server gets into this state, most links such as "Site" under "Common Tasks" do the same action...that is to revert the mode to "View" and return the same page I was just on with no changes effected.
DNN 4.6.2, SQL Server 2005 Standard Edition
I have also previously experienced a situation where my "Edit Text" option did not appear on the triangle menu for some pages. I don't recall how I solved this, but it may have been related to me trying to edit pages that were copies of other pages.