Nothing unusual, no pattern.
I've turned on historical graph but don't hold out much hope of it helping.
i think I am left with 2 choices now, convert to railo or upgrade the box to win2k12 and switch to iis.
Railo, not because I am taking my bat and ball and going home but simply because I have I don't exprience this problem working with the standard tomcat/mod_jk install on other clients. And additionally I have more control over the tomcat which gives me more options to solve this problem (e.g changing to mod_proxy_ajp)
IIS/W2k12 This is the other option.
I am not really happy with having to use either option and now I need to weigh up which will give me stability faster.