black screen after the first play on android

Hello.

I'm beginning android game making but I have a little problem : the remote work fine but if I test with an apk, the first play after the install work fine but the game stay froze on a black screen if I try to lunch it again.

My phone is a motorola defy (mb525) with android 2.1.

I thinked it was maybe the apps not closing but it don't show in the running processes.

Any idea?

PS : my next step is trying to upgrade to 2.2 Froyo, maybe it is a compatibility problem.

Thanks