"Step over" acts like "step into"; "step out" acts like "continue"

I think this problem started when I installed XCode 2.3. The Step Over button in the debugger window now acts like Step Into, as in if I try to step over a function call I end up inside the called function. Likewise, the Step Out button acts like Continue. As you can imagine this makes the debugging process rather more interesting than I prefer.

Anyone else seen this kind of misbehavior?

900 MHz G3 iBook Mac OS X (10.4.7)