VB Express program quited automatically?

Hi,

I developed a program using .net 2.0 with Vb express. Basically, the program uses multithread for computation. Once it finished, it pops a messagebox in the thread, letting users know it finished.

I just found this:
if I let it run at night, the second morning, I found the program automatically quited. No error message, no nothing. So, I do not know the result. I did this many time, all quited. I'm sure no1 else exited the program. Very weird. Just like the program quit running itself, although it is supposed to show the msgbox.

Anyone had this problem Is it possible because of Multithread Can I pop up msgbox in multithread

thanks

GT