Access denied for administrator for various processes

Using Commerce Kickstart and Aegir, and Drupal 7.38. My customer complained today that she's been unable to post pictures or display a particular view. She is logged in with the "administrator" role, selects a view that is role permitted (administrator), and Drupal seems to redirect the query to the anonymous user, which fails with "Access Denied" message. The logs indicate that the issue is the "anonymous" that fails, even though she's logging in as "administrator".

We can duplicate this problem whether it's user 1 or a user assigned the "administrator" role.

1) I can change the view permissions to allow anyone with permission to view content, and the view works (anonymous user can 'view content"). If i change permissions to "administer content" or to a specific role, like "administrator" or "editor", the view fails as above. So, permissions based processes appear to be failing.

2) Flush Cache from the administrator menu fails as above. Flush Cache from Configuration >> Development >> Performance does NOT fail. The problem persists after flushing cache, so it's not a cache issue.

3) IMCE fails too, whether attempting to "File Browse" from the user's login screen or while adding content (selecting the image icon from the WYSISYG screen).

Adding content does not fail. This problem cropped up about 10 days ago, and there has been no system maintenance, no Drupal or module updates, although my customer is maintaining the site herself. We've looked for cookie problems, and there don't appear to be any. The problem exists for existing daily users as well as for myself, my tech, with new launches in Safari and Firefox.

Stumped and would appreciate any insight anyone could provide. We're going to compare file content, but there are 270 files, so its daunting. The site has been working fine for 6 months.