Thunderbird Intermittently Uses ~130% CPU and Stops Responding

Ubuntu 14.10 (64 Bit)

:~$ apt-cache policy thunderbird-gnome-support
thunderbird-gnome-support:
  Installed: 1:31.4.0+build1-0ubuntu0.14.10.1
  Candidate: 1:31.4.0+build1-0ubuntu0.14.10.1
  Version table:
 *** 1:31.4.0+build1-0ubuntu0.14.10.1 0
        500 http://mirror.internode.on.net/pub/ubuntu/ubuntu/ utopic-updates/main amd64 Packages
        500 http://mirror.internode.on.net/pub/ubuntu/ubuntu/ utopic-security/main amd64 Packages
        100 /var/lib/dpkg/status
     1:31.2.0+build2-0ubuntu0.14.10.1 0
        500 http://mirror.internode.on.net/pub/ubuntu/ubuntu/ utopic/main amd64 Packages
CPU description: Intel(R) Core(TM) i7-4750HQ CPU @ 2.00GHz

Thunderbird email client intermittently freezes and shows approx 130% CPU usage (viewed using top). Thunderbird's memort usage seems to sit on around 2% (8 GByte installed). When the thunderbird error occurs, the mouse moves but the system does not respond to mouse clicks. I can [Alt] [Tab] to other applications (e.g. top in a shell window) successfully. The mouse buttons work once I have [Alt] [Tab] away from Thunderbird. The freeze sometimes lasts for only 30 seconds. Other times, I end up re-booting after ~5 minutes to resolve the lockup. Thunderbird has two email accounts registered - 1 x POP account, and 1 x Gmail IMAP account. My .thunderbird folder is 1.7 GByte in size.

I have been using Thunderbird on 14.10 for 4 months, and for about 10 years on previous versions of Ubuntu, and have previously experienced no problems with Thunderbird.

The problem being experienced could potentially be related to the installation of recent updates to Thunderbird as the errors started in the last week of January 2015, shortly after some thunderbird updates were installed. Refer to following extract from /var/log/apt/history showing Thunderbird updates installed on January 22, 2015:

Start-Date: 2015-01-22 17:09:58
Commandline: apt-get upgrade
Upgrade: python3-problem-report:amd64 (2.14.7-0ubuntu8, 2.14.7-0ubuntu8.1), libevent-2.0-5:amd64 (2.0.21-stable-1ubuntu1, 2.0.21-stable-1ubuntu1.14.10.1), thunderbird-locale-en-us:amd64 (31.3.0+build1-0ubuntu0.14.10.1, 31.4.0+build1-0ubuntu0.14.10.1), thunderbird:amd64 (31.3.0+build1-0ubuntu0.14.10.1, 31.4.0+build1-0ubuntu0.14.10.1), landscape-client-ui-install:amd64 (14.01-0ubuntu3, 14.12-0ubuntu0.14.10), libssh-4:amd64 (0.6.3-2ubuntu1, 0.6.3-2ubuntu1.1), thunderbird-locale-en:amd64 (31.3.0+build1-0ubuntu0.14.10.1, 31.4.0+build1-0ubuntu0.14.10.1), variety:amd64 (0.5.1-0~484~ubuntu14.10.1, 0.5.2-0~489~ubuntu14.10.1), thunderbird-gnome-support:amd64 (31.3.0+build1-0ubuntu0.14.10.1, 31.4.0+build1-0ubuntu0.14.10.1), apport-gtk:amd64 (2.14.7-0ubuntu8, 2.14.7-0ubuntu8.1), apport:amd64 (2.14.7-0ubuntu8, 2.14.7-0ubuntu8.1), python3-apport:amd64 (2.14.7-0ubuntu8, 2.14.7-0ubuntu8.1)
End-Date: 2015-01-22 17:10:31

There are no thunderbird related errors showing up in dmesg.

If Thunderbird is started from a command line, there seem to be no useful messages/errors appearing on the command line.

Any suggestions regarding what is causing this problem, how to diagnose it further, and ideally how to fix it ? Is this a bug ?

Thanks,

Roy