Help! v2 window disappears after 4 minutes of running in Win7

 From:  XP5 (VICXP0518)
Hi Micheal,

First of all, great jobs is MoI, I love it and thank you for providing such wonderful nurbs tool for us ;)
But I was confused by a problem recently. It happens to v2 and I didn't try the v1 so dunno whether it dues to system affair. The problem is:
Whenever I launch MoI, it runs excellently and smoothly on my Dell Intel i5 laptop. But 4 minutes ie. ~240 sec. later (I get it with a timer), the UI suddenly disappears and can never bring back again!
Then I look into the task manager but it shows the moi.exe and moi_commandprocessor.exe is still there and seem still okay, but you know I cant bring up the window since it is only in the Process tab. When I shut down the system, MoI asks me whether to save the file was editing.
Such phenomena also features that:
a) Different MoI processes do NOT affect each other, several MoI just 'disappear' distinguish;
b) Window disappears at the 4th minute only when the window is showing. If I've minimized the window, it won't disappear from taskbar, but after the 4th minute I click the button on taskbar it disappears immediately.
c) It WAS okay in previous days but not recently, no major hardware or sys environment changed, small changes forgotten :(
d) I've uninstalled it, reinstalled, reactivated, but the same happens.
I cannot confirm the same problem happens to others, or is it a bug or config corruption. The system I'm using is: Windows 7 Ultimate x86 (32bit), Dutch/English both tried, ATI, Intel 4-core i5 processor, anti virus softwares disabled, no virus infected.

If you people have any ideas please tell me asap, I'm hurrying using the powerful and ever wonderful MoI, thanks!