Webmail problem?

[#1]

Does anyone else get -"your session is invalid or expired" when they log into the webmail? The folders appear then It kicks you out after displaying the message.
My webmail works with squirrel mail but the Roundcube client kicks me out every time.
Its always done this on 3 different PC's i have used?
Ant ideas?

[#2]

Does this happen with different browsers?
Are the time and timezones set on your PCs correct?

[#3]

Sometimes I send an outgoing email and instead of taking me to Sent items to show it has gone it gives me some message about my connection is invalid or expired and goes back to the Inbox folder.  Despite this if I check my Sent Items the email has gone.
This is unlike the usual failing of Plusnet's flakey webmail servers at peak periods (it is clearly them that is at fault and not the Ironport front end)  when you are happily composing an email and then it suddenly decides to log you off the server and give an error message.  At one time historically if you pressed the Back button you could at least get back to the email you were writing but could only then cut and paste it in to a new email in a new webmail session as the system had lost track of that session that you had gone back to with the Back button.  However more recently pressing Back does not work 97% of the time and you have simply lost whatever you were composing other than what is in Drafts.
At one stage I observed that having Save To Drafts set to 1 minute made the problem with getting chucked off the webmail system worse as it always happened as a result of trying to save a latest version of the email to drafts .  But the flip side of this of changing the save to drafts setting to 15 minutes to avoid the excess connection activity that causes the loss of connection means that you can then risk losing the last 15 minutes of your email.  This is equally maddening so it is a no win situation.
If challenged on this issue on the phone Plusnet staff always rather pathetically give the excuse that you can't expect their webmail platform to be as reliable or resiliant as Hotmail or Gmail and it is better to either use a Pop/IMAP client like Outlook or Thunderbird with Plusnet email or alternatively to use a professional webmail service that you can count on like Gmail.  This seems a very lame answer given that Plusnet is now one of the UK's largest ISP's and not the little hobby operation that it used to be back in the days of a certain Mr Lee Strafford.  However I fear that the poor quality excuse for doing nothing to address this issue by Plusnet staff does indded go back to a hangover from Lee Strafford's days as MD.