notification center plugin: ios 5 Twitter accounts are nil?

Question

I'm developing a notificationcenter plugin with theos, which is accessing the ios 5 build-in twitter accounts. My problem is, that the accounts i get from the os are nil. What am i doing wrong? I am first creating a ACAccountStore, than i ask for acess to the accounts and after completion i save the accounts in an NSArray:

accountStore = [[ACAccountStore alloc] init];
ACAccountType *accountType = self.accountStore accountTypeWithTypeIdentifier:ACAccountTypeIndentifierTwitter];
[self.accountStore requestAccessToAccountsWithType:accountType withCompletionHandler:^(BOOL granted, NSError *error){
if (granted){ _accounts = [self.accountStore accountsWithAccountType:accountType];
//now _accounts is nil, no accounts inside...

Hope you can help me,

bensge