Dragon causing *complete* system crash

I have narrowed it down to being Comodo doing this. Tried various combinations of programs and the bug is almost impossible to reproduce as it seems completely random!
It will always happen as follows though:
-Browsing as normal - I often have at least 25/30 tabs open
-Will click a tab to switch to
-Will have a brief stutter followed by my entire system becoming unresponsive
When I say unresponsive I literally mean that I have to go for the power button and do a hard reset!

The only non-comodo extension I am using is AdBlockPlus for Chrome

Firstly, any advice on this, is it a known bug?

Secondly any advice on performing a complete clean install with Dragon? I have tried doing a standard uninstall but wonder if that maybe misses some files?
Thanks in advance for any help you can offer!