I also have top line new machine, windows 7 (64 bit machine). I believe the problem is called memory leak. Software that does not handle releasing memory properly. That is a Microsoft word for the problem. Software reserves memory, for use, and after use should release, but for whatever reason doesn't, you will run out of memory. Also since icone not 64 bit version yet max memory is somewhere around 3.2 gigs of active memory, even thou your machine has more available. My machine currently has 16 gigs, but only 3.2 available for use on 32 bit software.
I have a gadget that monitors memory and if it hits 45% of memory used, Iclone shuts down. Not sure if windows shuts it down or iclone self-destructs, that would require memory dumps and alot of analysis.
In my short history of iclone use it appears after 3rd or 4th full movie export. I save often and after every major change ( _v1a, _v1b, ....)
Hope that helps