when i interview for developers (we are a C++ shop, mostly), i certainly expect people to understand the syntax of the language, but more importantly to me, to understand what the language is providing. what is OO, what does OO provide over functional...
in addition what is class hierarchy? what does it provide to the developer? what are templates? when are templates useful, and when should templates not be used, for example they should not be used to provide hierarchy (which i have seen done). what is overloading (other than syntactic sugar!), these questions can be answered for any OO type language.
another huge concept that most interviewees do NOT understand is exceptions. even the basic "throw and get out of the way" concept is lost on them. and they truly don't understand that exceptions decouple normal program flow from error recovery. i'll have them write a method that generates an error and they'll start by returning an error code!! that will pretty much end the interview at that point.
another area is order of construction of objects that contain members that also have constructors, as well as order of destruction of objects and what happens when a base class's destructor is not virtual.
and lastly, how do they hold up when trying to design an algorithm for a difficult problem. i don't even expect the interviewee to complete the algorithm, what i'm looking for is how they attack the problem, do they ask me questions to help themselves out, do they use the whiteboard to get an understanding of the problem... the individuals in our group do not work in a bubble and if you're not willing to ask for help when you're stuck, then i have no use for you...