iPhone 4 when launchin app black screen?

Hey folks,

A friend of mine has this issue with her iPhone 4.

Everytime she launches an app she gets a black screen.

After pressing the 'home' button and restarting the app,

the black screen vanishes and the app works like normal.

This started happening after installing the latest iPhone 4 update.

I can't really find anything between developers having similar issues with

their own apps or people just having unresponsive phones with a persistent

black screen.

Anyone have an idea what it might be and maybe even a fix?

Thanks in advance!