So it appears that our Trend Micro Officescan antivirus does not like running SW Simulation.
After much searching I managed to find the answer in the Knowledge Base - my bad for not looking there first and relying exclusively on Google!
Have since disabled Trend Micro and no error messages so far... will leave open a couple more days just in case though!
Attached file is from Knowledge Base answer for those in similar predicament.
FAQID__x326.pdf 15.8 KB
Knowledge base provided solution.