Constant problems with SquirrelMail

[#1]

For the last few days it's been pretty bad.
A] I'm constantly getting this message when trying to do various email manoeuvres:

ERROR
You must be logged in to access this page.
Go to the login page
... but I'm obviously already logged in!
B] The Side menu with the folder listing keeps disappearing so I can't navigate around.
Hopeless

[#2]

SquirrelMail works OK for me, apart from the well known slow response when operating on Inbox content. This takes 50-60 seconds for me - with around 220MB of message data.
No delays are apparent when accessing the mailbox via IMAP using Thunderbird on my PC?
Do you *always* have these problems or are they intermittent? Does a page refresh eliminate them?