Is there a virus going around making this happen to video games lol. I have seen alot of this latletly..
Your system specs would help as well.
Ram especially. Although I do not think that would make them minimize...
As MadMatt suggests about the error codes..
Right Click my computer..
Click on manage..
When the window pops up click the little + next to event viewer..
If you know what times these things happend see if there are any red or yellow warnings (or marks) pointing to a program or the system
Under Apps and Systems See screen shot below.