Members not staying logged in

I've got a super mod on one of my forums that is recently having trouble with my forum. She says that it won't keep her logged in. When she tries to view a thread, it directs her to a log in page.

When she logs in, she is ticking the box to keep her logged in permanently on her computer, but after the page refreshes, anything she clicks shows her as not logged in.

Has anyone else had something like this happen? Ideas?

Make sure that you have non-www redirect setup: [How to] Setup www.yourdomain.com or yourdomain.com (www vs. non-www) - With .htaccess 301 redirects

I've got non-www. redirected to www. Been like that for years. Did the changes to the .htaccess that vBSEO made with the 3.2 RC5 (or thereabouts) update (for the /forum/ folder) include something that might conflict with the redirect rule I have in place in the domain root?

You should apply the redirect BOTH in root domain and forums folder.

I thought folders inherited .htaccess rules from their parent folders. Why would I need to repeat the instructions in a child folder?

In case if you have existing .htaccess file in a subfolder, it overrides rewrite rules from parent .htaccess.