I've installed mRemoteNG v1.70 RC1 inside a fresh Windows 7 32-bit virtual machine, which has nothing else installed except VMware Tools.
After creating a single SSH connection, as soon as I try to connect, PuTTYNG crashes.
I used Process Explorer to save a full dump of the PuTTYNG process as well as what appeared to be the parent mRemoteNG process that spawned it. This was done at the time of the Windows prompt asking me to close the crashed program. You can download the archived memory dumps here:
Let me know if there's any other info I can gather, or any different moment to do the memory dump at. I'm not too experienced with Process Explorer troubleshooting of this nature.