After having Zoho Mail installed for five months, it has stopped keeping me signed in on both of the computers I use.

Every time I logon using the shortcut on my taskbar or a bookmark, I have to sign in all over again.

I tick the 'Keep me signed in' box every time, and I am opted to use Secure Access.

 I have tried opening Zoho Mail with either zoho.com/mail/ or mail.zoho.com/biz/index.do, and it has not made any difference whichever I use. 

It first happened on my netbook at the weekend, which made me think it was a problem just with that machine, but the following day it started happening on my desktop pc as well.

Both operating systems are Windows XP and the browser on both is Opera 12.02.

It has not made any difference whether or not I set my Opera preference to delete new cookies when exiting.

On both machines I have the following cookies set to be kept by Ccleaner:

accounts.zoho.com, mail.zoho.com, zmail.zoho.com and zoho.com.

I have tried not running Ccleaner  for a trial period, and that has not made any difference.

Can you please help cure this problem that is really beginning to annoy me.