Just got my iPod Touch 4th generation a couple of days ago.. and today I just experienced something new. My application's icons randomly do not appear. But the space is still filled with the app and it still has the name in text below the icon space.

E.G.: App A shows icon and name.
App B doesn't show icon but shows name.

The next time I open the same folder..
App A doesn't show icon but shows name
App B shows icon and name.

Now, I usually double tap the home button and close some applications that I don't want hanging around in the background.

Could it be because of that?

I did a "hold-sleep/wake-button-and-home" to power off and turn it on again. The problem is gone. But I'm wondering if there is a root to the cause and is there a way to avoid this problem?