My Thunderbird on this machine stopped working properly yesterday. It refused to download e-mails from my account - but it was seeing the correct number of e-mails on the mail server. It would not accept updates (it was at version 24.6 but would not accept the update to 31.3.0). In desperation I deleted the programme and returned to basics, downloading a 'new' version of 31.3 from the Thunderbird web pages. However, having completed the download, the updater refused to run. Meanwhile, Thunderbird on my other computer updated itself to 31.3 quite happily - both machines run Windows 8 (64 bit). However, my master e-mail files and records are on this machine so I am keen to ensure a working Thunderbird here. So far as I can see both machines have the same set up, the same anti-virus protection (Norton 360) the only obvious difference is that this machine has a Core i5 processor whereas the laptop is a Core i3. What do I have to do to get the updater to run?