RCU used to keep me logged in . Now every time I come back I have to log in. What's the problem here?

Also in a thread when trying to view pictures the arrows do not function any longer?

I notice that sometimes I open RCU, it says I'm logged in, but then when I click on my forums it logs me out.

When I come to the forums, it looks as if I'm logged out. Then I click one of the Log In links and end up in my profile where I'm recognized OK.
Today I went twice through the cycle of clicking Forums in my profile, and Log In on the forums page, before I'm recognized as Logged In in the Forums. Weird, inconvenient...

Using Firefox on Windows XP, both automatically updated.