Actually I've gained some experience with multiscatter since then...as far as I've gathered by now, two things are important with multiscatter that may cause it to crash - the type of model you use as an instancing model and the sheer number of instances that may cause RAM problems.
Using very complex models like evermotion trees or somesuch in thousands or even only in hundreds has caused my mscatter to crash repeatedly, replacing them with models like "itrees" and "igrass" worked perfectly, supposedly those models are somehow optimized for use with multiscatter. I'm not sure why it sometimes (in my case often) crashes with your normal models though.
Second issue can be sheer number of objects used by multiscatter, despite the marketing, multiscatter doesnt allow you to go into gazillions of instances completely unpunished. Specially in complex scenes where other objects may already burden your RAM, it can very easily cause a crash during the render itself (usually during LC calculation), so try looking into that as well.
Anyway, those are just my observations up to date, hope it helps.