Thanks marcel,
I've just been trying 4.2.7.7215 (on two different max installs as we were getting slightly different results on different PCs with v4.2.7.7127). The nightly build works better but is still not quite right I'm afraid.
My test scene consists of:-
build a sphere, apply vertex paint with say a white strip on black. Now add guides from surface and use vertex paint for distribution. On previous version this worked on one PC but not on another, but with nightly now it seems to only work if you select map channel 1 instead of vertex colour.
Now I go back down stack and add another vertex paint to say mapping channel 10, and up to top to use this on strand length modifier.
with latest nightly (7215) this works, but on 7127 it would crash.
My second test is a more complex full head groom built with an older version. This crashes on load on both the latest 4.2.7 versions (stable and nightly) and I'm fairly sure the crash is down to a length mod that uses vertex colour. It opens okay on v4.2.5 though.
Anyway, I hope this helps getting to the bottom of it,
Cheers,
Tom