After updating a batch of Windows updates, it seems the ntdll.dll version got bumped from 6.1.7601.188869 (modified 25/5/15) to 6.1.7601.18933 (modified 15/07/2015).Since then, !peb, !teb, !address and probably others have ceased to work for me because the _PEB and _TEB debug symbols are missing (same with _LDR_DATA_TABLE_ENTRY). I couldn't find any reference online for it, but perhaps my google-fu is just weak.
Did Microsoft remove the _PEB and _TEB symbols from the ntdll's debug symbols permanently?
windows;windbg;debugging symbols