Any programmer here?

Can anyone please explain me why this code sometimes doesn't work, or even crashes?

Boolean ptBluetooth_Enable (Boolean on) {
SvcCalledFromAppPBType *p;
DmSearchStateType stateInfo;
UInt16 cardNo;
LocalID dbID;
UInt32 result;
Err err;

// find prefs app
MemSet(&stateInfo, sizeof(stateInfo), 0);
err = DmGetNextDatabaseByTypeCreator(1, &stateInfo, 'panl', sysFileCBluetoothPanel, true, &cardNo, &dbID);
if (err != errNone)
return false;

// create param
p = (SvcCalledFromAppPBType*) MemPtrNew(sizeof(SvcCalledFromAppPBType));
p->cmd = svcCFACmdSetBtOnOff;
p->data.bValue = on;
MemPtrSetOwner(p, 0);

// run prefs app
err = SysAppLaunch(cardNo, dbID, 0, sysAppLaunchCmdPanelCalledFromApp, p, &result);

if (err != errNone || result != 0)
return false;

return true;
}