iPhone sdk will not compile if i use UITableView Group background color

Question

if i use grouped table view or just use this color, i get this compilation error:
The document "DetailedView.xib" could not be opened. The operation couldn’t be completed. -[NSCFArray insertObject:atIndex:]: attempt to insert nil.

if i use plain tableview it works fine.
also i tested on number of xcode installations and on different computers and still the same.

any ideas?