Bug reported by Wavez;

Leftmouse select option doesn't work with "Emulate 3 button mouse" option.
The latter maps middle mouse to ALT+leftmouse, frustrating loop select for
example.

Add tooltip to say this, made option to disable automatic on load (version
check) and made buttons redraw to show option being disabled.

Note; wrapping middle mouse to ALT+RMB will frustrate 1 button mices... the
current code for leftmouse-select is a hack at best, better do this good
when we have proper event handlers system.

source/blender/src/space.c

@@ -2349,10 +2349,14 @@ void drawinfospace(ScrArea *sa, void *spacedata)
 				0, 0, 0, 0, 0, "");
 		}
 		
-		uiDefButBitS(block, TOG, USER_TWOBUTTONMOUSE, 0, "Emulate 3 Button Mouse",
+		/* illegal combo... */
+		if (U.flag & USER_LMOUSESELECT) 
+			U.flag &= ~USER_TWOBUTTONMOUSE;
+		
+		uiDefButBitS(block, TOG, USER_TWOBUTTONMOUSE, B_DRAWINFO, "Emulate 3 Button Mouse",
 			(xpos+edgsp+(3*mpref)+(4*midsp)),y3,mpref,buth,
 			&(U.flag), 0, 0, 0, 0,
-			"Emulates a middle mouse button with Alt LeftMouse");
+			"Emulates Middle Mouse with Alt+LeftMouse (doesnt work with Left Mouse Select option)");
 		
 			
 		uiDefBut(block, LABEL,0,"Middle Mouse Button:",

source/blender/src/usiblender.c

@@ -259,6 +259,11 @@ int BIF_read_homefile(void)
 				}
 			}
 		}
+		if (G.main->versionfile <= 235) {
+			/* illegal combo... */
+			if (U.flag & USER_LMOUSESELECT) 
+				U.flag &= ~USER_TWOBUTTONMOUSE;
+		}
 		
 		space_set_commmandline_options();