my program flow is here

display self(this);
press key

deleteAll();
append(image);
.
.
(some image);
.
.
append(image);
display self(this);

it is work fine at the emulator. but if run at the real phone(N90)
the problem is appear.
after press next key --> show "no data" --> show "image"
anybody can tell me why "no data" screen will appear??

i also switch screen to "waiting screen" before deleteAll();
it is work fine at the emulator. but if run at the real phone(N90)
the other problem are appear.
after program running it will stop at the "waiting screen" !!
why ??