Took me ages, had me scratching my head for months 
Almost dumped Ableton Live and returned (somewhat unwillingly) to Cubase. 
Then.... After a lot of fiddling I sussed it. 
Under the OPTIONS menu in Live there is a option for DELAY COMPENSATION which is ticked as standard. UNTICK IT!!! 
and remember to run the VIRUS VST in "LIVE MODE" 
I NEVER had any issues with Virus and Ableton now, it all works like a dream . 