Don't use GetBoolArg() and mapArgs; use one or the other.

main.cpp

@@ -3455,7 +3455,7 @@ void BitcoinMiner()
     SetThreadPriority(THREAD_PRIORITY_LOWEST);
     bool f4WaySSE2 = Detect128BitSSE2();
     if (mapArgs.count("-4way"))
-        f4WaySSE2 = GetBoolArg(mapArgs["-4way"]);
+        f4WaySSE2 = GetBoolArg("-4way");
 
     // Each thread has its own key and counter
     CReserveKey reservekey;