Changed slow buttons behavior.

Marlin/Configuration_adv.h

 #endif
 
 // Control heater 0 and heater 1 in parallel.
-#define HEATERS_PARALLEL
+//#define HEATERS_PARALLEL
 
 //===========================================================================
 //=============================Buffers           ============================

Marlin/ultralcd.cpp

 #else
 volatile uint8_t buttons_reprapworld_keypad; // to store the reprapworld_keypad shiftregister values
 #endif
+#ifdef LCD_HAS_SLOW_BUTTONS
+volatile uint8_t slow_buttons;//Contains the bits of the currently pressed buttons.
+#endif
 uint8_t currentMenuViewOffset;              /* scroll offset in the current menu */
 uint32_t blocking_enc;
 uint8_t lastEncoderBits;
     WRITE(SDCARDDETECT, HIGH);
     lcd_oldcardstatus = IS_SD_INSERTED;
 #endif//(SDCARDDETECT > 0)
+    #ifdef LCD_HAS_SLOW_BUTTONS
+    slow_buttons = 0;
+    #endif
     lcd_buttons_update();
 #ifdef ULTIPANEL    
     encoderDiff = 0;
 {
     static unsigned long timeoutToStatus = 0;
     
-    lcd_buttons_update();
-    
     #ifdef LCD_HAS_SLOW_BUTTONS
-    buttons |= lcd_implementation_read_slow_buttons(); // buttons which take too long to read in interrupt context
+    slow_buttons = lcd_implementation_read_slow_buttons(); // buttons which take too long to read in interrupt context
     #endif
     
+    lcd_buttons_update();
+    
     #if (SDCARDDETECT > 0)
     if((IS_SD_INSERTED != lcd_oldcardstatus))
     {
         newbutton |= EN_C;
   #endif
     buttons = newbutton;
+    #ifdef LCD_HAS_SLOW_BUTTONS
+    buttons |= slow_buttons;
+    #endif
     #ifdef REPRAPWORLD_KEYPAD
       // for the reprapworld_keypad
       uint8_t newbutton_reprapworld_keypad=0;