Steve, this is probably what you meant ...

stepmania/src/arch/ArchHooks/ArchHooks_darwin.cpp

@@ -255,7 +255,7 @@ void ArchHooks_darwin::MessageBoxOKPrivate(CString sMessage, CString ID)
         IgnoreMessage(ID);
 }
 
-void ArchHooks_darwin::MessageBoxError(CString sError)
+void ArchHooks_darwin::MessageBoxErrorPrivate(CString sError)
 {
     CFStringRef error = CFStringCreateWithCString(NULL, sError, kCFStringEncodingASCII);
     ShowAlert(kAlertStopAlert, error, CFSTR("OK"));

stepmania/src/arch/ArchHooks/ArchHooks_darwin.h

@@ -14,13 +14,14 @@
 #include <SDL_thread.h>
 #include <queue>
 
-class ArchHooks_darwin : public ArchHooks {
+class ArchHooks_darwin : public ArchHooks
+{
 public:
     ArchHooks_darwin();
     ~ArchHooks_darwin() { }
     void DumpDebugInfo();
-    void MessageBoxError(CString sError);
 protected:
+    void MessageBoxErrorPrivate(CString sError);
 	void MessageBoxOKPrivate(CString sMessage, CString ID = "");
     MessageBoxResult MessageBoxAbortRetryIgnorePrivate(CString sMessage, CString ID = "");
 };