Why can I not enter Edit Mode on my custom pages in SharePoint?

I have a very strange issue I just cannot figure out. I am not able to enter Edit Mode on my custom pages. Appending my URL with ?ToolPaneView=2 does nothing. Manipulating the Site Actions button to custom content and changing the MenuItem_EditPage to get the Edit Page button back bring the page into some kind of edit mode with the "Exit Edit Mo开发者_开发知识库de" button but still no toolbar or ability to manipulate web parts. Anyone seen this before?

Thanks

My experience was that the page was created with the SharePoint Server Publishing feature turned on. The site feature was later deactivated and the page could not be edited. Re-activating the feature enabled editing.

I had it once when the page was checked out by the system user.

Discard the current check-out (and lose changes) and I could edit the page again.