Using Thunderbird email client,i REPEATEDLY get a screen saying the Security Cert is invalid and asking to make and store a permanent exception.It refuses to accept this exception and the screen just repeats again and again til insanity sets in! The screen won't close or cancel. Thunderbird Forum says its the Avast mailshield (cert.issuer) and the Cert.Manager seems to confirm this. Following Avast Help procedures I tried to Export/Import the MailShield,but on trying to import into TB,it just says it already exists there. Can someone PLEASE help with this problem. I have Avast Free AV and the Avast Secure Browser.Both are completely up to date.