weird background in grouped table cell

We use in our application cells in a grouped tableview as buttons. Therefore we set a backgroundimage to look the cells like buttons. We used the following code:

cell.backgroundColor = [UIColor colorWithPatternImage:[UIImage imageNamed:@"bg_gradient_mainmenu_2.png"]];
cell.textLabel.textColor = [UIColor whiteColor];
cell.textLabel.highlightedTextColor = [UIColor whiteColor];

which looks like this

The weird thing now is that it works for just some devices with different OS Systems. It definitly doesn't work on new iPhones 4.

Does anyone has a clue how s开发者_开发知识库olve that problem?

for iphone 4 you can set the backgroundView. The group table behaves erratically while working with table cell background.